Problem with static pages paths in Jekyll on Gitlab pages

Recently I’ve migrated my blog from GitHub to GitLab. On this one I have pages for every category of my posts. Into Jekyll documentation there is the sentence:

Unlike posts, pages by default mimic the source directory structure exactly. (The only exception is if your page has a permalink declared its front matter — in that case, the structure honors the permalink setting instead of the source folder structure.)

Into my blog repository I have categories directory. Into this directory I have files with pages code - every for one category. As far as I understand documentation, file from path: categories/ should be on address (that’s my blog address). And when I was on GitHub it worked on this way. I don’t want to add permalink to every category page in front matter. It shouldn’t be sollution. Can anybody help me with my problem?