Immersion is really the best way to learn [any language]. You either use it or you end up forgetting the vast majority.
Note: in Spain, “que tal” doesn’t actually mean “what’s up” like the teachers tell you it does. It means something more literally like “how are you”, and is just used conversationally like English people say “what’s up”. Hence, if someone asks you “que tal” and you reply “nada” it becomes rather humorous for them.
