I've found that supplementing Duolingo with yiddish teaching materials, including books, helps a great deal with reading and
comprehending Yiddish. I've bought a few books but I have to admit that I was not prepared to use them when I started with Duolingo yiddish, they were way advanced. But, a book like the dictionary and phrasebook shown in the below article is a good
choice for browsing, picking up some translations and maybe a phrase at a time.
This article reviews six popular (?) yiddish textbooks.