I accidentally deleted some files in var/lib. I don't know what I have deleted. Gnome-terminal too then disappeared since I messed up with Gnome-Purge. I then installed xterm using TTY. But then when I try to install some package, Unmet dependencies 'Try apt-fix broken install' with no package name. I do not want to reinstall Ubuntu.
I installed i3 with sudo apt-get install i3. But if I try to launch it via terminal, it says another window manager is running. In older versions of Ubuntu, there was a round button at the login screen in which we click to select WMs. But in 18.04, there is no such option. How do I launch i3 without making the mess like changing stuff in a file?