My computer is unusually slow and some applications won't work.

My computer also will only show capital A's when i'm online sometimes like: AAAAAAAA instead of what it's actually supposed to say. It's super slow and Applications like Chrome and Spotify won't even operate when opened. System Preferences too. Safari is okay, but sooner or later it'll freeze. Streaming is impossible, and even writing this is taking a while. And clicking on some buttons on the upper toolbar just don't work. What do I do? Should I just bring it into the Genius Bar?