The previous site had urls that started with /nl/ to indicate the language. But it's a single language site, so in the new site there's no need for that.
I wanted to add those URLs in the Redirects module (e.g. /nl/diensten to /diensten), but that wasn't possible.
Error message "The Redirect From URL already exists as a page path. Redirect not added."
I would expect that the redirect would be handled, but it's not. I looked at the module Jumplinks so I could use wildcards, but not sure if that's even necessary to solve my problem.