What will happen when you jump into a volcano? would you sink or what?

I think you might sink slowly, but you'll also burn. 

You wouldn't sink. Your lungs would either:
A.) Disintegrate
B.) fill with smoke
or C.) they would Char.
All of these would result in death. So basically, jumping into a volcano will destroy your lungs before anything else  

Eating right and exercising daily

There is tumerous cancer, kawaski disease and more.