Do not be afraid to change this settings. It will continue working as it is, or with luck working better
If something bad is happening once you have gave a try to that, I'm writing you the steps to undo this changes.
Try it, and if you have troubles to boot, you can remove this additional settings at boot time. Imagine it is not booting anymore :
In GRUB menu at the first line (default) press the "e" key. It will show you all the command line to run your OS. You will see things we have added by hand there, you can remove things we have added and next do Ctrl + X to run. It will boot as before. Next we will remove definitively what we done for test and
-> A less risky solution for you, if you are afraid to practice grub at this stage with permanent things
Swith off your PC - fully.
Start it and inn GRUB do press the "e" key. It will show you all the command line to run your OS. You will see and will be able to temporary update :
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force"
or with a other try :
Next do Ctrl + X to run it.
Next do your shutdown tests.
If its not booting, no stress, it was temporary and nothing will happen. You will reboot it and all will be as before.
My opinion is that the kernel you are running now is in a conflict with your hardware.
If this what we are going to try is not working, i will advise you to upgrade your kernel (possible with a well done GUI tool with no worries)
Do not be afraid to practice, its a way to learn