Ubuntu 18 doesn't boot after AMD driver install

I newly installed Ubuntu and so I wanted to install the drivers for my AMD rx580, downloaded the file and installed it via this guide here

I tried both the normal and pro install but both gave me an error. Tried like the first answer here said, rebooted and got a white rectangle in the middle of the screen and some text wasn't displayed correctly. So I uninstalled the driver like in the first link described and wanted to reboot, but now my PC won't boot correctly and I'm stuck at a black screen with: "A start job is running for hold until boot process finishes up"

At this point I couldn't find anything on google.

Edit 1: After the mount command nothing else will show up in the command line (except the line to enter my next command) and on tip of the white box with different options there is still written "read-only". After that if I try the amdgpu-uninstall commad it says it couldn't find the command even after I navigated to the files I downloaded (maybe it needs to be executed in another folder but I don't know which ). I also tried this with the pro command.

You need to uninstall the drivers you manually installed and let ubuntu-drivers choose and install the right ones.

Since you can not access the terminal right now. You need to boot into recovery mode and drop to a root shell to do that.

Please follow the steps below:

1. Reboot your machine and hold the Shift key as soon as you pass the BIOS logo to access the GRUB boot menu. You might need to repeat this a few times until you succeed and see the boot menu.

2. Select advanced options and hit Enter.

3. Select the second option with (recovery mode) in front of it and hit Enter.

4. Wait until the machine boots and another menu appears. Choose the option with drop to root shell prompt in it and hit Enter.

5. Press Enter when it says press Enter for maintenance.

6. Once you are presented with a command prompt, write the following command and hit Enter (this will give you read and write access to your system):

   mount -o rw,remount /

7. You will need now to uninstall the AMD drivers by following the corresponding instructions from the same guide.

8. Now you need to let ubuntu-drivers tool install the suitable driver for your card, to do so pleas write the following command and hit Enter:

   sudo ubuntu-drivers autoinstall

9. Reboot your system.

Notice:

• If Uninstall script fails in step 7. You could try How do I remove the proprietary ATI drivers? instead. However, I would strongly advise to first try the uninstall script that came with the original driver installer.

• You might as well need to repair broken packages, if any, by following the steps under option #2 in this answer and also try failsafeX option if necessary.

• If all goes well and your system boots normally again, you can later search for a specific compatible AMD proprietary driver and install it if you wish.