Ubuntu 16.04 in boot loop [duplicate]

I recently tried to update all my stuff with sudo apt-get update, but after my computer restarted I could not log in. If I type in the correct password, the screens turns black, and has an error message in the top right corner:"System problem detected. Do you want to report the problem now?" However, I cannot interact with the error box, either to click cancel or report problem, and the screen blacks out again, bringing me to the gray gnome login screen again. I've tried all the fixes on this website (https://www.linuxslaves.com/2016/05/3-ways-fix-ubuntu-gets-stuck-login-loop.html?m=1) but none worked; I tried these through recovery mode's root command line. I do not have Nvidia drivers, and I cannot access the command line with Ctrl Alt F1 from the login screen, as it freezes or does not do anything. Worth noting that the Ubuntu GNOME I run was not originally the GUI I used; it was installed after Unity. It always had a few errors (frequent error messages, sometimes the time settings menu in the top right, or random letters were invisible) but not like this. Unfortunately, I'm not sure what version of Ubuntu I was trying to update to, but I can get that info if told how. I also have Windows 10 installed, but use it very rarely. My laptop is a Dell Inspiron. Thanks.

Edit: Used a live USB for the command line, and none of the fixes in the first article work. For the first, there is no .Xauthority in ls -lah. For the second, it runs but there is no output. For the third, I do not have lightdm installed to begin with. I also tried using boot-repair; it claimed there was an unknown error while repairing. However, after restarting, I sort of logged in. The screen was all black, with the same error box that later disappeared, except for the time and text saying "activities" in the top left corner. I used Ctrl alt T to open the terminal and it appeared against the black background. A few seconds after, everything disappeared and returned to the login screen. I feel this a graphics error, but a selective one. At the login screen I still see my name, a white box (no profile picture in it), and the time. If I click near the top right bar where the Wi-Fi icon would be, I can interact with it, but most of the text does not appear. I also tried use a previous kernel version (4.4.0-89) to no avail. My current version is 4.4.0-97.

Edit 2: I created a "good environment" as described here by mounting by Ubuntu partition while in a live USB. (https://askubuntu.com/a/1006982/701605) I then ran fixes 2 and 3 for the previous link; I think re-installing lightdm did the trick, as it was my original desktop manager instead of gdm3.

First create a "good environment" (not sure with the textonomy), it means that you have to create a link/connection between your installation and Live USB OS before trying that out. You can check that here. You can take refrence from this answer on how to make good enviroment.

Then follow steps given on linuxslaves.com .