What does this phrase mean and how to use it？---“as so often"

What are the differences and how to use these words "учёба" "изучать" "заниматься" I am confused about these words, they seemed have the same meaning,but I don't know how to use them correct. Please add examples)))

“What are you up to？” Is this sentence asked when you refer to someone who may have bad intension of planning to do something or it has other meaning according to different circumstances?