Back to Linux …
It's very simple method how to do it
Boot into grub, select single user but do not press enter.
Press e to go into edit mode.
Scroll down to the kernel line you will boot from, it starts with "linux /boot/vmlinuz-……."
Scroll to the end of that line and press space key once and type init=/bin/bash
Press Ctrl X to boot
# Remount / as Read/Write
mount -rw -o remount /
# Change the root account password with
# Change any other account password with
# type new password, confirm and hit enter and then reboot.