I want to upgrade my python to at least python 3.7.5

The newer version that I have of python is too old to my applications, is only 3.6.0, so I need a most recent version to use my apps.

Now I'm not running anything, so can upgrade the image without any problem.

You no longer need to ask to have your system image changed -- you can change it yourself from the "Account" page. There's more information on this help page:

Worked for me, thanks

Glad to hear that you made it!