User Management issue

I did setup web+server on my machine then tested User Management but I'm getting error:

• I created a Admin
• Then created Manager and you can see screenshot of Manager
  
• Then logged with this manager and trying to create a user but I'm not able to do that:
  
  What should I do?

I think you mixed up your screenshots.

let me give you the steps:

• I logged as a Admin
• Then created a Manager with Device limits: -1 and User limits: and I did not check any checkbox from permission list
• Then I logged in with this Manager and try to create a End user/Customer.

So screenshot which I shared it means second one is a first and first one is a second. Let me attach you again:
Manager user edit mode:

End User/Customer Add user screen:

Just tested and it works fine for me on a clean Traccar 6.11.1.

Let me share you my version:

If I would need to update then how would I do that?

Check the documentation.