I'm considering if I should throw away my smartphone and change it into a dumb phone.

Why might you want to do this?

Because i think it keeps me from studying

It has an off switch.

make rules for yourself, or shut it off, set a timer

Even a screen lock with a PIN that operates when the screen times out would make a psychological hurdle, but really, why worry? If you think noodling around on a phone is more important than studying, you can always get a job flipping burgers when you flunk out of school. (In my day it was marijuana and rock music.)