How to start your Mac into safe mode to fix start up issues?

How to start your Mac into safe mode (safe boot) to fix start up issues?

If you want to start your macOS without any interference from the start up applications, you must boot from safe mode (or safe boot). If your Mac suffers from interrupted booting, or slow booting and you don’t know the reason, you have to boot into same mode to isolate your system and uninstall the suspected application.