Ubuntu Admin User Add
Hi! This tutorial will guide you step-by-step on How to Create a SuperUser/Amdin User in Ubuntu GNU/Linux.
Especially Relevant: this is the right procedure to follow Only in Case you do Not Dispose of Any SuperUser on System!

Reboot your Ubuntu System.
On GRUB Splash Select > Boot in recovery mode.
Select > Drop to root Shell.
Create SuperUser with Admin Privileges.
adduser [myUser]
Choose a Passowrd for your New User.
Then to Add User into the sudoers Group do:adduser [myUser] sudo
Finally, Reboot your Ubuntu System.