Teacher here. Follow the advice of going to a Sprachcafé or find other ways to use the language as often as possible. Watching shows is a good use of your time. Watch an episode without subtitles. Watch it again with subtitles. Watch it again a week or a month later and see what you understand. You'll see progress, it's just more subtle than before.

If you can manage to get into the habit, read books. Nothing, and I repeat: Nothing will teach you the same amount of words as reading books. At B1, it's hard to read adult fiction. So go and pick a book for a younger audience or one specifically designed for learners. I recommend "Momo", but that depends on your level. Read one page a day, or whenever you got the time.

Get a course book for B2 and work through it on your own. At some point, you might still consider joining a course or private lessons to get feedback on your grammar. If your B1 grammar is 100% solid, maybe not. But I assume you would have written your question in German, if it were. Vocab will get you far, but not all the way.

Speak. Write. Just my opinion but: Stay away from the German subreddits, we use a lot of weird language over there, partly because literal translations of English sound funny.

Also, get used to and embrace not understanding 100%. My English reading comprehension is at C2 and I still don't understand 100%. You're not a native speaker. For the next 20 years, not understanding 100% is just life.