Usually if you get the grub boot loader and it doesn't show any boot options, it's because grub was not installed correctly and/or the partition that it is supposed to be on has changed or does not exist. It can also happen if you install Linux to one drive, but the boot loader to another by accident, whether EFI or MBR/Legacy mode.
You can normally fix your booting/bootloader/MBR/EFI it by chrooting into your root partition:
#become root
sudo su........
Usually this is because when you created your user you added a user but didn't create their home directory and/or for some reason your .bashrc and .bash_profile in ~ (home) is broken/missing.
In your home just create the following files with the following content to solve it:
.bashrc and .bash_profile.
To apply it just relogin/start a new bash session
# .bash_profile
# Get the aliases and funct........