venting

Arch is not a distro I'd recommend for beginners. Try something like Mint or Ubuntu. Even Debian has a gentler learning curve.

If the installer simply unmounted the partitions, they should (I think) still be there. They just need to be re-mounted.

It sounds like you deleted the EFI partition. The BIOS checks for a partition with a special filesystem (basically FAT32) to load the OS bootloader. That's where it gets the information about the OS name to show in the BIOS boot selector. If it's gone, the operating system won't show up, and the system can't boot.

People more knowledgeable than me have offered better advice than I could. Just wanted to stop in to say that sucks man, I'm sorry you're struggling with it. Folks are right though, arch is one of the most technical and complicated places someone could start :(

It's unclear from your comments how much personal data may have been lost. I hope not much- in the future before you make big changes be sure to back up your personal data, even if its just copying stuff to a flash drive

I'm wishing you luck with your fresh start on a new distro. Most distros these days are super straight forward, plug and play operating systems with a graphical installer that does all the work for you- arch is one of the handful of exceptions

Just today i deleted a separate partition on my disk and i couldnt access arch anymore, it wasnt showing on the bios.

If it wasn't your Arch installation, I'm guessing that that was maybe the EFI boot partition, since that's the only thing I could think of that'd affect the visibility in BIOS.

https://en.wikipedia.org/wiki/EFI_system_partition

is everything just gone now?

I've never used the Arch installer, but I'd guess that it doesn't wipe everything without some kind of warning.

If you mean, by "unmounted", "deleted", then yeah, it probably deleted them. It's maybe possible to re-detect the location of filesystems on the drive if the data hasn't been overwritten yet.

If you don't mean "deleted", then it's definitely there.

In Linux, run lsblk. That'll list all the partitions it can see.

You can manually mount 'em doing something like this (if /dev/sdc1 is in there):

# mkdir mountpoints
# mkdir mountpoints/sdc1
# mount /dev/sdc1 mountpoints/sdc1

Then look at 'em.

# ls mountpoints/sdc1

And when done:

# umount /dev/sdc1

If you find your partitions, then you can re-add 'em, probably to /etc/fstab, which is just a text file in a particular format that tells a Linux distro what mountpoints to mount at boot. I don't know if Arch does anything special here.

That's just part of the installation process. You need to nuke it 3 times before you get to the real installation.

(Sorry about what happened...)

Create a FAT32 partition 256-512 MB in size for UEFI, preferably at the end or start of your partition table by chrooting as described by others and running grub-install /dev/sdX (or /dev/nvmen0pX or sth like that if you have an NVMe drive) on your newly created partition, then update-grub, also as a root. For ease of use you can use something like GParted live, but I'm not sure if it provides a terminal that can properly chroot into your arch installation.

Then check if your BIOS "sees" the newly created UEFI partition and if it's set as the default boot option.