how do I get multiple administrators to access my limesurvey system, but without seeing each other.
* version free

I fully agree with you friend.
The problem I even started with another call, is that we are a matrix with more than 100 branches and they want this possibility to be able to create the question themselves.
the problem of seeing each other is exactly what you said ... sometimes they can delete other questionnaires.
Is there a solution other than the docker?

You mean super admin ?

You can't

Else : Group member can only see own group : www.limesurvey.org/manual/Global_settings#Security

Yes. I will be the super administrator.
And whoever asks me for a questionnaire, I just want to provide the infrastructure.
The person himself will create your questionnaire, but you will not be able to see those of others.
But I still haven't seen the admin configuration correctly. In other words, whoever I define as a questionnaire creator, can see others.

Then : you can just give Survey creation right to other user.