It depends on what you mean if it drivs and wont change gears it can be a cloged filter or valve body or snycronizers going bad and the trans need to be replaced or repaired. if it wont come out a gear from park it may be frozen.
You will need to check your fluid level and the screen. You may also have a a clog filter, valve body, or the snycronizers might be going bad. If that is the case it needs to be replaced.
I once had a car that started out by shifting gears rather hard, then quit shifting after second gear. It turned out that it was time to have that transmission rebuilt
