Can't install any program on Linux

[GipsyDanger120]

Hey guys,

 

I'm fairly new to Ubuntu. I have a HP G14 laptop that has Lubuntu installed on it. The computer has been doing great, new RAM and SSD was installed. First weeks I had a problem with the screen being too dim, so I turned to forums to see what could be the problem, that problem was resolved by apparently changing some lines of code in: /usr/share/X11/xorg.conf.d. While doing that I had to use sudo to be able to change that file (I think I updated another file someplace else but can't remember). 

 

Now, since I did that I haven't been able to install or remove a program, I get the following message every time (the following quote I took from running sudo apt-get install -f, which was prompted by the Software Updater since It was not able to upgrade Lubuntu):

Quote

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libkeybinder-3.0-0 libllvm6.0 libzeitgeist-2.0-0 python-dbus python-gi
  python-gobject-2 python-xdg python-zeitgeist zeitgeist zeitgeist-core
  zeitgeist-datahub
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
  linux-image-4.15.0-112-generic
0 upgraded, 0 newly installed, 1 to remove and 58 not upgraded.
1 not fully installed or removed.
After this operation, 8,411 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 209799 files and directories currently installed.)
Removing linux-image-4.15.0-112-generic (4.15.0-112.113) ...
/etc/kernel/postrm.d/initramfs-tools:
update-initramfs: Deleting /boot/initrd.img-4.15.0-112-generic
/etc/kernel/postrm.d/zz-update-grub:
Sourcing file `/etc/default/grub'
/usr/sbin/grub-mkconfig: 1: /etc/default/grub: #: not found
run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 127
dpkg: error processing package linux-image-4.15.0-112-generic (--remove):
 installed linux-image-4.15.0-112-generic package post-removal script subprocess returned error exit status 1
Errors were encountered while processing:
 linux-image-4.15.0-112-generic
E: Sub-process /usr/bin/dpkg returned an error code (1)
 

It has something to do with the DPKG, but what even is that? 

Thanks in advance guys!