Where can I learn Yiddish? Is there some whats-app groups or online learning ?

Time is extremely valuable and it takes a long time to learn a language well enough that it can be helpful (especially Yiddish, where every place has a different dialect, for Yiddish is not really an official language, but a "conglomerate" or "cholent" where every slang enters and changes, and you'd have to learn them all for it to be useful). Accordingly, Hebrew, which is a mitzva, as well as being helpful in all Torah study- is surely worth the time and effort. On the other hand, during the long exile, in many European countries, Yiddish used to be important in some circles to participate in Torah classes. It's already been several decades, that it's no longer necessary, and anything worthwhile in Yiddish has been translated to Hebrew or English. In short, it's better to invest your time in Torah or ideological pursuits rather than using those precious months to study a galuti and language which won't last and won't contribute that much to you.