I did it!
I made all the skills turn gold (Level 5).
Thank you to DuoLingo for creating the app, and thank you to all the moderators/native speakers who answered questions and replied to comments, but especially to Jellei.
Goodbye to the Polish course, and hello again to Hebrew, Greek, Spanish, French, German, and Czech.
Kocham sowę! Jellei jest wspaniały. Trzymajcie się. Teraz koniec dla mnie. Pa.
both are in Locative. as usually when something happens "in" something.
adjective/pronoun has to have the same case, gender and number as the noun.
but mój has moim as both instrumental and locative.
hints in Polish course are like dictionary- show some possible options. (and AFAIK they stopped adding case hints so there could be some possible cases missing)