I'm stuck in a login loop on my first account. I can, however, log in with the guest account and with a new account I created on terminal.
This is the log errors, please help me understand what is causing the sigterm.
Since you don't know exactly where the problem is, create a folder at your desktop (or documents) and move there all hidden files and folders from your home folder (every single one to be sure, even the ~/.local folder) and then reboot (those which are need will be recreated on reboot with default configurations, so if you need for example the chromium bookmarks and configuration just move back the ~/.config/chromium folder or the ~/.mozilla folder for firefox etc.). If everything works and you don't need to restore anything delete the folder you created after.
I had the same problem some time ago, for me it helped to login via a terminal and execute
$ sudo chown ~/.Xauthority
See also the answer this question on AskUbuntu:
The .Xauthority (not .xAuthority) file can be found in each user home directory and is used to store credentials in cookies used by xauth for authentication of X sessions.
[...]
So, if you are not the owner of this file you can't login since you can't store your credentials there.
Hope I could help.