We bought an Amana Big Oven 5.14 from a friend. It takes forever to preheat, and I have to set it on 450 degrees in order for it to reach its proper temp, and that takes about 1 1/2 hours. Then it took me 3 hours to bake a cake. Pizza cooks from the top only. It seems that the baking element is not working properly, but we can not see where the elements are to check them.I can not see elements nor figure out how to check them. How can I get my oven to Preheat properly and bake as it should?