windows 10 - How to remove Administrator rights?

So for the longest time I only had one user on my computer. It obviously has administrator rights. Now since I am studying IT I learned that it is way more secure to use the PC with as less rights as possible, to give malware less power if it happens to affect my system.

I went into cmd, run it as an administrator and wanted to make a second user. I called it Admin and added him into the "Administratoren" group, thus giving him administrator rights.

net user Admin /add
net localgroup Administratoren /add Admin

Now I wanted to take away the administrator rights on my main user "Rismosch"

net localgroup Administratoren /delete Rismosch

It succesfully did remove the user "Rismosch" from the group, but I was not able to log into my user again. In the end I added "Rismosch" back into the group, because I couldn't access it otherwise:

net localgroup Administratoren /add Rismosch

Now "Rismosch" still has administrator rights and I don't know how to get rid of them, without preventing me from logging into the account.