there is a sefer (i forgot the name) which teaches the basics of yiddish, and very easy to learn, its a small sefer, but is wide, kind of like a sideways notepad, and is purple and pink on the front, which helps a lot for basic yiddish, but to be fluent, buy a sefer called likutei sichos, and sit and learn the sefer with a chavrusa who knows yiddish, and words which you dont know, right the taitch above the word.
I did this, and after a year i was fluent.