Baking heeeeelllllppppp! :D?

ok so its been a year or 2 years since i started baking and learning, i have a gl baking pan, usually used to make lasagnas, its 9" x 9" and like 3 and a half " tall, but i use it for baking brownies, i always er the pan before i put the mix in and put it in the oven. buuuttt i dont always leave them in the oven for the amount of time said on the box, i like em' kinda creamy and squishy lol but still, when i leave em out to cool off, then proceed to cut them into squares, teh ones at the edges always stick... is there some other thing i can use as substitute to er, that will not make them stick?? thankyouuu~~ annddd what would happen if i were to put strawberries in a cake mix, and put em in the oven..? will the strawberries come out tasting bad..? or all shriveled by the heat?