Startup stuck on /dev/nvme0n1p2: clean ?? HELP!

I’m a new user to Ubuntu and this is my last resort to try and fix my computer. I hope someone can help me.

I have a Dell Inspiron 15 5000 , Intel core i3-1080p. Its brand new and it came with Windows but I have since installed Ubuntu and have been using it fine for I guess over a month. Everything worked fine, the installation went perfect.

I wanted to change the purple default login screen to a picture or a different color, so I looked up if you could do it. You could, but it had to be done through the terminal thing. This is the tutorial I followed to change it:

I followed the instructions precisely and everything looked exactly as they said it would, but I had to restart it for everything to take effect. This made sense, but when I restarted it, it blinked the desktop once and now I’m stuck with a black screen that says “/dev/nvme0n1p2: clean” etc at the top, along with a bunch of other things like “started user manager for UID 121” and “started session c1 of user gdm”. (I tried to add a photo of it to this post but it was too big apparently.)

The screen it’s stuck on normally shows up when I start the computer, and then it will go to the desktop and work fine, but now it just stays there. I can’t do anything with it. I’ve tried things like going through the GRUB menu, checking the boot menu, and nothing works. I’ve done so many different things I’ve lost count. I’ve called people, no one supports Ubuntu/Linux. I’m completely stuck. PLEASE HELP! I’m new to this and I leave for college tomorrow and this is my computer that i was going to use. I desperately need a solution.