Hello @zolzol, I hope you are doing fine.
You can go to your theme and edit the code. The button should be on a file called product-template.liquid (or something similar). From there, you just need to find the code that it's related to the product description and the one related to the button. You will have to switch their position.
I can help you but I will need store access or at least you sending pictures of the file.
Hope it helps and I wish you a lot of sales.
Sara from The Support Heroes.