Broken CSS and Theme – can't fix

I selected a theme that had something at the bottom I didn’t like. I found what I thought were the lines of code and deleted them. Now my site has no theme at all and I can’t fix it. I’ve tried activating a different theme and I still can’t get my site to have any theme at all. I’m ready to give up. Can you help me before I throw in the towell. I still have a day to get a refund.