Hello,
I would like to change the "Super user" name to "Admin" in K2 Items comments, where it says "super user"
So when I made test comment.

I opened k2 item and on right settings I changed author alias to "Admin" and also I changed in Joomla usernames the name of Super user to Admin already but it still keeps showing in items detail page.

thank you for any help.

K2 inherits Joomla! 's name.
If you changed it in Joomla!'s user it should work.
Double check the K2 Users and check if the Admin name is indeed inherited.

Finally clear your browser's and Joomla!'s cache.

I dont understand at all what you wrote, could you pls tell me step by step what to do?
Im not a guru to understand all terms :(

Change the Joomla! user's name.
Then go to K2 -> Users to see if the name has been properly changed.

I hvae this solved thx only the last issue everytime i create category it show IF I CLICK from module on sidebar positioncategoies, url with ../content/ + name and ID/
:(
it's not the template they told me to ask you, gavick.com

the url i tested now is this:
mywebsite.com/blog/content/33-test/

when I click from categories what shows when i created in menu manager of joomla it is ok:

mywebsite.com/blog/test/
:(

If you want the content/id part to disappear you need to map this category into a menu item.
This is how Joomla! works. You cannot have a clean url (no prefixes/ ids etc ) without a menu item.

From menu it works ok but this is a module created which display categories, this is generating its own /content/ID it doesnt depends on menu, its a moduls from K2