Hide a slicer along with RLS

Hello everyone , i hope you are doing well.

I have a 3 page company's report , i used a slicer (the same one for each page ) for each department .

I want to give access (RLS) to each department , the CEO and external users . 

Each department should be able to see their numbers and the company overall numbers ( without seing / selecting others department).

The CEO should be able to see everything.

And the extern user should only see the company's overall numbers ( hide the slicer)

I have used a RLS but it only show the KPI for each department and not the company's overall (while hiding others departments).

How can i be able to give access to the report for each department ( and them be able to see the company overall numbers)

and how can i hide the slicer for externe users?

Thank you for your help!