I'm at a similar level you with finishing B1 and starting my treck towards B2. For me personally I finally had the breakthrough a few weeks ago where I could listen to any song, speech, twitch stream, or media in German and pick the individual words spoken about ~90% of the time even if I didn't know what the word/phrase meant or could even spell it. I can now listen to natives speak and not feel overwhelmed.

If you have already had that breakthrough, then I think the biggest help would be to constantly listening to media like twitch streams, having a german music playlist, and subscribing to fun subreddits like r/ich_iel. I've found that on off days when I don't want to study or can not, incorporating those methods keeps me from regressing. Anything passive really that you enjoy or can incorporate would probably be the best way to stop any regression. Heck, maybe even just do a Duolingo placement test and use it to study vocab when on the bus or something.