Simple request I've had for years

I've wanted to use Outlook (again) now for quite a few years, but I cannot figure out how to do a completely fresh restart. 

Many years ago I work with Outlook for a while. Then I switched to Gmail. I'm thinking of going back, but don't want have all the structure I set up back then. I cannot figure out how to delete all my setup and mail in the cloud. 

Can anyone give me some quick help?

Thanks and stay safe.