I need help to start my MacBook Pro

Try an SMC reset:

How to reset the System Management Controller (SMC) on your Mac - Apple Support

Try starting up in Safe Mode:

Use safe mode to isolate issues with your Mac - Apple Support

If neither of those work boot into Recovery and Reinstall Mac OS.

About macOS Recovery - Apple Support

Try Single User Mode (hold command-s keys)

At the prompt, enter this command:

/sbin/fsck -fy

Press the Return key.

This will check your directory and report that it was OK or repaired. Then enter this command to startup normally:

reboot

Run Apple Diagnostics  

Press and hold the d key on startup:

https://support.apple.com/en-us/HT202731

If none of those work make a Genius Bar appointment for a free diagnostic:

Genius Bar Reservation and Apple Support Options - Apple

What is preventing your MacBook from starting? When you attempt to start it, do you see the Apple logo? How far does it get before failing to start?

In that case, I'd highly recommend trying what "macjack" suggested.