How do I restore the Grub menu?

Since you lost your password, it sounds like you just need to change your password to get a normal boot. To do this hold down your shift key during boot up. Select recovery mode (which is usually the second entry). Wait for boot up process to complete. There will be a list of options. The one that you want is the Drop to root shell option so press the down arrow to get to that option and press enter to select it.

The root account is the ultimate administrator and can do anything to the Ubuntu installation (including erase it) so be careful with what commands that you enter in the root terminal. If the file system is mounted as read only, you will need to enter: mount -o rw, remount/ in the terminal Now to reset the password, type: passwd username where username is the user name you want to reset. Substitute your username. You will then be prompted for a new password. When you type the password you will get no visual response acknowledging your typing. Hit enter when you are done. You will be prompted to retype the password. Do so and hit enter again. Now the password should be reset. Type: exit to leave the terminal.