Ok first, I think this should be posted in the “Focused Critique” forum or “WIP” forum not here.
But we all make mistakes so no problem.
Your model has a style! If you were to animate this dude, inside a world which matched his body style (a cartoony square and blocky world) then that would be a great animation! So, good model.
Now if you’re asking how to get rid of the square blockyness, I’d suggest sculpting perhaps? Or using proportional vertex editing to puff out his chest? Either would work.
Just an idea, if this was my model, I’d keep him as is, and use him as a abstract human. Too me, he looks really cool! Like the fact that his arms and hands are like TOTALLY out of proportion. And his head is great! He would make a good Frankenstienish monster!! Oh man you could have fun texturing him.
Just some things to think about.