Hey there. This is my first project concerning wood, and even then, I'm remodeling a bookcase. My problem is I used an angle grinder ( was desperate cuz nothing else was working) and it worked stripping the paint off but I have these gradual bumps all over the wood. As a beginner, sanding seems like the right thing to do. Though, I know if I go about it wrong, there is no going back. Like don't know what kind of sander. I heard a belt sander is a little more aggressive which might be useful in this situation but not certain. I am afraid I already messed it up enough as it is. Any advice would help, all ears.

lemme know if you have any questions.
Best, Aidan.