Anyone familiar with code?

[XFFA.IR Bot]

Hello, someone created a custom style for me. The design(s) is great, but I was looking to adjust the banner at the top of my forum to make it smaller. Tried a few things in the templates and it did not work. The creator told me that it was only possible if the code was adjusted. I'm somewhat of a novice at these things.

Would someone be able to help me? If PM is more suitable, I would prefer that.

Thank you for your time.