My macbook is not turning on. When i press power on fan starts running at high speed

Yes I get that. You need to see if it steps in to Diagnostics mode. Refer below.

1. Hold down On/Off button of your Mac and simultaneously hold down 'D' key.
2. This should kick start the machine into diagnostics.

Refer below:

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

Have you tried to run diagnostics at startup and seen whether it move to the diagnostics setup?

Else startup the machine keeping 'R' held down. This will make the Mac go into Recovery mode. You may want to re-install the OS.

I would go with the Diagnostics first though. Recovery is a little advanced as there is a race condition from the fan's going into overdrive.

Hi,

I think your MacBook Pro has hardware related issue. You should make Genius Bar reservation if your neighborhood retail Apple Store is open or take your MacBook Pro to opened Apple Authorized Service Provider to be examined it or send your MacBook Pro to Apple Repair.

https://www.apple.com/retail/geniusbar/

https://locate.apple.com/findlocations

https://support.apple.com/repair

If this isn't working I suggest you give a call to Apple Support If u have an Apple Care valid.

else talk / chat with them - they have been known to be pretty helpful.