I don’t meet your criteria for someone who started learing later. Howqever if you have a passing familiarity with Yiddish I have friends who have furthered their comfort by both listening to shiurim and reading childrens books.
stay away from guides to teach Yiddish, because today (at least among chasidim) there is no formal Yiddish teaching with grammar and such. You pick up what people around you say. So for example wheras in “real” Yiddish as in Hebrew nouns are either feminine and masculine. In spoken Yiddish you say what “sounds right” so an emphasis on grammar is a bit misplaced
Good luck