Also, I frequently watch German Youtube gamer because I love watching let’s play videos and they’re easier to find than the movies (I tend to be very picky about the genre when it comes to movies)
so far I don’t understand 75% of what they say, but I do catch a lot of the repeating words or slangs they use. But I’m wondering if this is efficient for a beginner level for me? or should I use English subtitle until I’m at a certain level?
Try it both ways, and see what you prefer.
The German subtitles will help you pick out the words you couldn’t hear, while the English subtitles will help you with meaning.
If I don’t understand what’s going on in a video, I start with the English subtitles, and switch to German later, to see how much more I’m starting to pick up.
At 75% understanding, you might want to start with German subtitles first, and see if you are able to read along in the German text, then switch to English subtitles for a second pass.
Experiment as you go along! The techniques that work for you on Lingq will change as your knowledge grows, and as you explore different kinds of content.
I use the Language Reactor extension in my browser. While watching YouTube videos it displays the target language in large subtitles near the bottom of the screen, and smaller subtitles in my native language right below those. I generally follow along reading the text in my target language to help me pick out the words and phrases I’m hearing, but if I need to I can glance further down briefly to see the English translation.
The gaming videos you watch may not have both of those sets of subtitles available though. You’d have to install Language Reactor to see for yourself.
“so far I don’t understand 75% of what they say”
An important part of the comprehensible input learning method used on LingQ is not just finding media that interests you, it’s also important to listen to audio sources and watch videos that you can understand fairly well, with only 20%-30% unknown content at the most. You need to give yourself something that builds on what you already know and are comfortable with.
Hope that helps.
Yes, thats a very good idea! Actually, it’s better to try to avoid translations as much as possible, try to watch videos that are tuned to your actual language level, than progress gradually. What is good is to have German subtitles, not English or other language. Like this you can focus on both pronunciation and writing. And of course, vocabulary 
Wie Deutschen WIRKLICH reden 
Unless you have a rare brain, you won’t learn another language when you have subtitles in a different language. Your brain will instead automatically focus on the subtitles and on the language you know better. This is why, for example, an anime fan can watch thousands of hours of anime subtitled in their own language and never learn more than a few random words of Japanese. (There are some studies saying that, for example, autistic people’s eyes focus on different sections of the screen than a non-autistic person’s, and so they may have an easier time learning a language when translated subtitles are on the screen.)
The reason for having both text and audio in the same one language is that your brain will automatically match sound to the written word. Your brain is so powerful at this that you can teach illiterate people how to read simply by turning the subtitles on. Some words you know better in the spoken, some you know better in the written, but your brain will “knit” the two together and improve both skills. Having German subtitles on will also improve your general reading speed. And, of course, many times it is easier to “piece apart” stuff like unknown compound words when they’re written down, and it’s also easy to pause the video then type or copy paste the unknown word into a dictionary, compared to if there are no German subtitles and you’re trying to type something up by ear.
As others have said, you also need to find the genre in German with the most cognates to a language you know. As an example, if you are learning Italian and know English, you are going to find the most cognates in academic texts like business documents (legal contracts) and news articles, because English took so much academic vocabulary from Latin / Romance languages. There is a ton of misinformation out there regarding what is “easy” for beginners. You are going to have a far easier time reading a news article about politics or economics in Italian than you will reading an Italian children’s book or a “Hi, my name is…” travel phrasebook.
I have never studied German, but I’m fluent in Swedish and Japanese. Children’s books often actually use quite obscure vocabulary (how often do we really say words like “He was crowned”, “taffeta”, “dragon”, “a horse carriage”, “a plough”, etc?), or contain a lot of puns and jokes, making them harder to understand. I’ve found that one of the easiest genres to understand is “poorly written” Romance series, so you might want to try those.
I find travel phrase books useful to create language islands.
Example: After importing and reading a few articles that talked about health and healthcare, I jumped to that section in a phrase book, and read it twice, without even trying to memorize anything but just noticing similarities (cognates), funny false friends **1, etc..
I reread it a few days later and was gladly surprised to see how much I had remembered (especially the one about **1). I do that in thin layers/easy passes, almost effortlessly, and I trust repetition to do its magic.
-—
**1 In Spanish, “Tengo un constipado” means “I have a cold”, not a clogged bottom 
(that’s ”constipación”).
Sorry, I didn’t mean to say that travel phrasebooks are useless. But if you are starting out learning a language, you should begin something that has a much higher percentage of cognates, so that much less of each sentence and paragraph is new vocabulary. As you mention, the medical field seems to be a good pick for many languages. I don’t speak Spanish at all, but I was able to read a college textbook about child development in Spanish while looking up almost no words, because words like “gestation” are the same as in English and so much academic vocabulary in English was taken from Latin and Romance languages.
In Swedish, the medical field actually doesn’t have many cognates with English, instead they have created or directly translated words. As an example, English and Swedish both say “blood pressure” with exactly those two words, but “pressure” aren’t cognates. Meanwhile such basic words as medicine (“heal stuff”), hospital (“sick house”), ambulance (“sick car”), etc, aren’t cognates, and there are several phrases which are confusing to learners (at an actual hospital they don’t say “blood test”, they just say “test”). They aren’t hard to learn, but it is still different from them being as easy as cognates. I imagine German is similar. In that case the best subject to start with for German would not be medicine.
In languages where there are very few cognates, such as Ukrainian, you can still find texts where there is higher number of cognates with English than normal, for example reading political news about America where there will be a lot of famous American people, places, company and even sometimes job names (such as “the president”) taken directly from English.
I think it can be helpful to use both. It might be good to just go through with English subtitles to get a better understanding of what is going on in the video. Then also use the German subtitles to get a sense of the pronunciation. At your level, like you said, you’re not going to understand much, but having run through it once in English should help out a little, at least to know what is going on at any given point. You may still not make a match to the German words just yet, but it could help.
Once you get to a higher level you will be understanding more and more of the German subtitles and also be hearing the correct pronunciation. Even still the English subtitles can help to orient.
One thing I wanted to point out is that often the subtitles do not match the audio (Netflix is fairly notorious on this). This, to me, is a probably if they don’t match very closely. First of all, especially at lower levels it is confusing as the sounds don’t match what you are reading (whether you can understand it or not). It is then not helpful with you putting sound to what you are seeing. So, for learning, make sure you are looking at matching subtitles. At a higher level, when this is the case, I often find myself just reading the subtitles and ignoring what I’m listening to altogether.
Another interesting observation. A couple of series I have (or had) been watching, I had started with German subtitles. However, subsequent seasons ended up being on platforms that didn’t have the German subtitles. Only English. Because I was interested in the series I went ahead and finished them, and kept the English subtitles up too. In some ways this worked better than I thought. I could focus on listening (and not the subtitles), and only refer to the subtitles if I didn’t understand what I was listening to. So this can be a good exercise too (but maybe for a time where you are understanding 75% or more).
I also second the suggestion of using Language Reactor, at least for movies. It’s nice to be able to pause between sentences and really study a movie/show. Repeat the lines, etc.