Can't change background on London theme

I just hopped onto Webflow and I cannot change the Hero Gradient Image background. In the backgrounds section I uploaded my own file and it is not popping up. Changing the color isn’t doing anything either. (I want to get rid of the Purple Orangish gradient where it says Worlds Most Secure Wallet)

https://preview.webflow.com/preview/digital-marketing-6511ca?utm_medium=preview_link&utm_source=designer&utm_content=digital-marketing-6511ca&preview=405d72ad88190e843620792d590ec3cc&workflow=preview