I know several languages on various levels:

* Polish native
* English C1-C2
* German B2-C1
* Russian B1
* Spanish B1

I have tons of opportunities to speak to natives:

* English - quite a few people at work (though very mixed origin: USA, Canada, UK)
* German - I have been living in Germany for 8 years now
* Russian - my wife speaks exclusively Russian at home (to me and our kids; I talk to all of them in Polish) and we spend ~1 month each year in her hometown
* Spanish - every now and then I meet Spanish people where I live and there is a chance for a longer conversation

I can usually eventually communicate what I want in all of those languages. But I don't feel like I'm getting any better in neither language. I'm not taking a course or any other more structured approach as currently, I have other more pressing issues in my life. Still, I'd like to make the best use of the time I have with natives. Without turning the encounters into a lesson, that is.

If I had to narrow down the things I'd like to improve I'd go for:

* grammar (e.g. prepositions and articles in German, declension in Russian)
* vocabulary (nothing specialized, just every-day topics)
* pronunciation (not perfect, just being consistent and sounding clear)

It's about improving confidence and fluency.

I don't have to work on everything at once. If there are any ideas to prioritize things, then I'm happy to hear them.

So, how to get most language learning benefits from frequent, casual conversations with natives?

Cheers!