ISO: A brownie dilemma

You all seem so knowledgable, I hate to insult any one, but I can not for the life of me make a descent brownie.I have tried numerous recepies and even boxed mixes the results are stll the same. They look like lave for the first inch around the edge of the pan ,are as hard as rock and half cooked in the center. My sister was with me after I had surgery this summer and was able to make a perfect batch in my oven using the same pan I use every time. I am desperate have considered giving up tryng to make them all together and just buying them at the local market/bakery. Any one know how to fix my brownie dilemma.

Wendy