>Is this addon compatible with the 5.8 version ?

NO
It is supported only 5.6.

>Is it possible to hide the counter for simple visitors and show it for administrator ?

I can not understand it. Please tell me again.

Hi,
It's noticed "compatible : 5.7.2+" ....

For the second question : in my old site in 5.6 I'm using "simple hit counter". With this addon I can choose to show or not the counter to the visitors. If I choose "hidden", the administrator is the only one who can see the counter.

May be, it is not my block.

My form block is here.
https://www.concrete5.org/marketplace/addons/extended-form5/...