When I used Ubuntu 17.10 at first I had problems updating with
sudo apt-get update && sudo apt-get upgrade I had major broken dependencies errors, so I rewrote the sources.list. I also blocked software sources and libraries that caused those problems, and it kind of worked.
I quickly realized that this was a wake-up call.
I went through the terminal to install Ubuntu 18.04.
After that the GUI install failed. Now I do not remember the whole process, but in general I changed the sources.list according to Stack Overflow answer/guide for these kind of errors like
The following packages will be upgraded or
E: types of errors.
After I finished installing Ubuntu 18 I get only a terminal prompt, so I started to install the desktop environment.
After a full night of handling errors on every command I've input almost
sudo apt-get install ubuntu-desktop or the tasksel tool, I don't know.
Anyway after one reboot it finally worked somehow, but after I installed the GUI at the login screen to the desktop environment where there is a field asking for a password my password does not work although it worked before I installed the desktop environment. So I use grub bootloader to reset the administrative password by following this question's answers: How do I reset a lost administrative password?, but for some reason it doesn't reset the password or it doesn't save it or maybe it's a hashing problem. I even tried the answer by keepitsimpleengineer, and it's only output login while nothing is happening.
I have a lot of stuff on that machine, and I went a bit dumb because I installed the 17.10 release. In any case I will be happy for an answer. I have access to the terminal only through recovery mode, and I'm locked out my desktop.