Yiddish is closer to german than it is to hebrew. its a Germanic Language mot a Hebraic Language
that being said, the easiest way to learn is to listen to it being spoken especially about a topic that you know about (ie the speaker tell you before what he is speaking about so you can get ideas what is being said)
there are also some old Yiddish movies that would help you and give you visial clues of what is being said so you can figure out the words.
Just going to a shiur and listening to a speaker likely wont work unless you know what the topic is