Edit: my dad tried to help troubleshoot my computer and now all of the filesystem is gone and the partitions are completely broken. I don't think there's any coming back from this, so I'm just booting up from Ubuntu from a separate USB stick.
I had successfully dual-booted Windows with Ubuntu before this happened. I was trying to temporarily boot up with Tails and accidentally deleted my boot option for Ubuntu. I clicked "Load defaults," hoping it would restore it (which is a terrible idea in hindsight), and ended up accidentally deleting all my boot options. As far as I can tell, all the files for necessary for booting up are still there, it's just the path to the bootup files that's deleted.
I'm using a Dell Latitude E7440. When I try to boot up using my USB stick (which holds an image of Tails), it just takes me to the GNU GRUB command line. When I type ls, it says: (proc) (hd0) (hd0,apple2) (hd0, apple1) (hd0,msdos1,gpt1) (hd0,msdos1) (hd1) (hdq,gpt2) (hd1,gpt1)
After I type exit, it says no bootable devices found. When I press F1 to retry boot, it takes me back to GRUB. F2 takes me to bootup options.
Under these options, I can click a button that says "add boot option" which is on the same screen where I accidentally deleted the boot options before. When I do that, I can write a new name, below it displays "File System List:" with unchangeable text that starts as "PciRoot(0x0)/Pci(0x1D,0x0)/USB(0x1,0x0)..." The line below it reads, "PciRoot(0x0)/Pci(0x1F,0x2)/Sata(0x2,0x0)..." Then below that I can select a file. When I browse for a file, I can select from FS0 and FS1 file system- the latter is empty. FS0 contains subdirectories .disk, EFI, SYSLINUX, LIVE, UTILS. It seems like EFI is the most important of these from what I've read, so I'll describe that directory a bit more. It has two subfolders, BOOT and DEBIAN. BOOT contains BOOTIA32, BOOTX64 each with their own .EFI and .PNG. It also has GRUBX64.EFI. The DEBIAN subfolder has GRUB.cfg, and a GRUB subfolder. The GRUB subfolder has files SPLASH.PNG, UNICODE.PF2 and subfolders I386-EFI and x86_64-efi.
I've tried creating boot options that point to BOOTX64.EFI and GRUBX64.EFI and naming them "ubuntu" and when I tried to use that boot option, it just took me back to the GRUB command line.
I would greatly, greatly appreciate any help getting my computer to successfully boot up again to using any OS. Thank you so much for any help you can give.
