tldr: What is your current language learning right now? Maybe you need to tweak? How much listening are you doing–I hope LingQ stats aren’t indicative of what you’ve done. Listen more. Worry about grammar less.
I think rather than asking about pushing yourself and the effort given…What exactly are you doing on a day to day basis? You’ve learned other languages, but you say you’ve usually done them in the country. What are you doing now for German considering you are not in the country? Perhaps you need to tweak how you’re approaching learning the language? (Keep in mind these are just thoughts aloud, and may not apply to you or your situation and that I have no idea what you are currently doing).
And for how long each day is your language learning time?
I notice you have just under 10 hours listening time in LingQ. I imagine you’re doing some listening outside LingQ, but how much? If you truly have only 10 hours listening, then that is clearly too few, but you should also be nearing 300 hours (if I go just by LingQ’s suggested? numbers). Reading is great an all, to acquire the vocabulary, but you also need listening to help cement things…and if you ever wanted to communicate, obviously you’d need to have lots of listening.
You also mention having trouble learning words that are not similar to your other languages. I also have that problem as I’m sure everyone does, it will come eventually. Maybe you’re being impatient? The other thing is, while you may be having difficulty getting those new words to stick, you are reinforcing the words you “know”. I’m sure there are plenty of words you barely “know”, and every time you read, listen, write, speak that words you are making it that much more ingrained so that you don’t even have to think about the translation. It just is. That is super helpful, in particular, trying to understand quickly spoken speech. You need to speed up that whole process.
You mention about forgetting grammar points. Maybe my thoughts will change, but I frankly wouldn’t worry about it all that much. I think if you are actively sitting down with grammar book and trying to “learn” grammar, that might not be the best approach. If you see something in your reading and listening and feel compelled to look up and understand why things are a certain way, by all means then look that up. I think it makes more sense in understanding and really learning the grammar when you can tie it back to something you know. And in the end, does the grammar really matter so much? Over time, will you not simply get better at it because you’ve read and listened to these patterns? Certainly this is all debatable, but to be honest I frankly don’t remember any grammar rules from school. The last bit of grammar I learned was probably in elementary or maybe middle school. Certainly by high school we weren’t being taught “grammar”. In our writing, things might be corrected and as we read or listened things start to sound right or wrong when we try to utilize the language. I think mostly these patterns you just learn and mimic.
OK, enough babbling by me.