I understand in English

Please tell my, this is correct, the phrase “I understand in English”
Or to place the word “understand”, using a different alias in everyday speech?

I speak English - better. But I think it can be: I understand English. But you needn’t ‘in’, besides an object: I understand this word in English, but I don’t understand it in German.

You could just say, “I speak English” or “I know English”.

thank you

I don’t understand this sentence in English: It never does, does it? I can’t translate it into Russian. What does it mean?

“It never does, does it?”

This is a phrase used to express that something rarely works out. The phrase is usually rhetorical, but not always. I usually think of the phrase as be used to comfort someone.

Examples:

A: I tried my hardest, but it didn’t work.
B: It never does, does it?
A: No

A: I tried to use the computer, but it wouldn’t start
B: It never works properly, does it?
A: Nah

A: No matter what you do, you’ll can’t beat it
B: It never stops, does it?
A: No

I’m sure others could come up with more/better examples.

Thank you!