How to remove something from the slug/url I got entries in the folder /cms/web/videos/ and the url display this: http://domainname.com/cms/web/videos/barco-auro.

I want it to be this: http://domainname.com/videos/barco-auro.

How do I create clean URLs? I don't find anything on this, or nothing that helps my problem.
In Craft 3 under your section config change the URL config

https://docs.craftcms.com/v3/sections-and-entries.html#sections

SEE: Entry URI Formats

You can select what template it should render and what URL config you want

Failing this you can use something more advanced:

https://docs.craftcms.com/v3/routing.html#advanced-routing-with-url-rules