ew83 cooker keeps burning food?

i have a few problems with my hotpoint ew83 cooker , the first thing that happened was that i had food in the oven , when it had finished i turned the main oven off and left the food in , but although i had turned it off the fan stopped but the element stayed on which resulted in burnt offerings for dinner. today i put something in the main oven it should have been in for 35 minutes on 160degrees , but after 20 minutes at 160 degrees the food was burnt. can anyone give me a reason for this