What should be the relationship between an adminstrators table and users table
From what I can tell from your image (please post ddl instead), there is no relationship between adminstrateur and technicien_sav. If you add an attribute created_by or administered_by in technicien_sav, there would be a relationship.  Since this attribute most likely is not part of the key for tech... , it would be referred to as a non-identifying relationship. Example:

CREATE TABLE adminstrateur
( adminstrateur_id ... not null primary key
, fullname ...
, ...
);

CREATE TABLE technicien_sav
( technicien_sav_id ... not null primary key
, ...
, adminstrateur_id ... not null
      references adminstrateur (adminstrateur_id)
);


I prefer using the same attribute name throughout the model, names like id, name, etc are IMO to vague. Even better is to use names from the domain of discourse, but I have no idea what the might be in your case.