It only shows me 6 relations

Where are you seeing all 28 when editing the post?
Is the setting for 28 in the main settings page?

Also are you using the block? If so, there is a bug in the block which I will fix in the next version. But, you can manually install and test currently.
https://github.com/WebberZone/contextual-related-posts/releases/tag/v3.2.3-beta2

Yes, I select the 28 when editing the page, but when viewing it, only 6 appear.

Yes, I am using the block, I will wait for the official update.

I would also like more content to be related, in my case it always shows me the same relationships, I would like the option to show randomly, I understand it in showing randomly but it always shows me the same

I released the new version yesterday. Can you please confirm? It was a bug I fixed in that one

Yes, it’s already solved.

but how do I make various relationships appear to me, the same ones always appear

A few things to tweak – toggle the use content and title setting. Use the match by tags and/or categories.

The former changes the list of posts – if you have very heavy content posts I prefer to keep this setting off as it limits it to title.

The tags/categories setting restricts what the plugin finds as contextually related to the same set of tags or categories which allows more relation. Note that this works well if you’re pulling through a tonne of posts vs very few.