No, screenshots will not clarify anything.
The complete output of;
however will go a long ways toward clarification.
Rambling about how you will "simply deny permission to users" is pretty clearly and concisely indicates a total lack of understanding the system you are screwing up. How on earth are you going to do that while dismantling the system set up for that purpose?
The suggestion that you reinstall and try doing it correctly really is the best answer you can possibly get if you refuse to give needed information on your system.
The user root does not, in any version put out by Canonical or any respin based on Ubuntu, have a set up account by default.
There is a sudoers file that is configured to give users in the sudoers group elevated privileges that equal the privileges of the user root.
A quick look at your /etc/group contents will give just about everyone with a modicum of Linux systems a pretty good guide to your problem.
Like most problems I have on my installs this is not actually a Linux or Gnu problem at all. It is a PICNIC problem.
I like to think it is a great way to learn. You must, however, be willing to;
A>listen
B>do some sensible reading of documentation
Admittedly a lot of the documentation that actually is correctly informative is written in what is to me a foriegn language, Geek. You do have to do some translation and this takes some time.
It is much easier to find blogs to follow written by other people that also know little or no Geek but do know a lot about writting. At least 95% of those sites will get you into trouble with bad advice and, worse, bad step by step instructions.