So I wanted to change my username and… I miserably failed…
I started to follow the steps here
So I edited /etc/passwd replacing my username by the new one:
nano /etc/passwd
Except that now I can’t use my own password (and can’t use sudo)… is there a way to fix what I just did?
Hi @kerry.perret, and welcome!
I’m not going to be the one to say it, but you shouldn’t have done that! 
I’m guessing, if you can remember what files you edited, you can edit them again, this time from a live ISO environment back to what they were.
Alternatively, you could from the said live ISO environment, enter a chroot environment, and create a new user for you yo use.
Alternatively, you can just reinstall.
Well I actually read this bit… except that it was too late when I did…
This is what I ended up doing up doing ~~ things are back to normal now 
I’m very glad to hear that! I’m also glad my advice worked. Now, what have you learned from this exercise?