Theromstat or timer issue

When I use the dryer on "optium dry" like for cottons, the dryer heats but the timer does not move. When I use the "timed" drying, it does not get hot but the timer moves. So I can use it but I have to dry every thing on the max setting or it 1) doesn’t get dry and 2) it takes a long time and 3) I have to remember to check it otherwise it will run forever. Please help I need to get this fixed but can’t afford someone to come out here.