Brain damage can sometimes be reversed but not always.
If the brain damage was not very severe then the brain may naturally repair itself to where it was before.
But if your brain suffered severe trauma then it's very unlikely that you'd recover from the brain damage and if you did recover from the severe brain damage then you'd be very lucky.
Most people who get very severe brain damage either die or have a severe mental problem for the rest of their lives.
And in some cases when people have very severe brain damage they live in a vegetable like state and cannot do anything at all but lay there on life support.