As long as the laptop boots, you should be able to switch to a TTY console, where you have a complete shell interface to your system after logging in (in said TTY console). So, being greeted with a login screen or something is a win here - but you’re very vague in your report.
The GUI is only just a program and has nothing to do with your boot options in BIOS or bootloader (like grub).
Using CTRL-ALT-[F1-9/0] you can switch between your virtual consoles and on only one of them your GUI is running.
You can use any other one to change anything on the system from CLI.
You should also be able to stop the current GUI/X11 Session and directly start the window manager you wish - temporarily to fix your system, if you’re not confident in the CLI.