My s3 wont turn on

I switched off my mobile after that I tried to Switch it ON but it stuck on Samsung logo, I tried holding up keys *volume up+power+menu button* but nothing happens I tried to holding up keys *volume down+power+home button* and there is option like

WARNING
A CUSTOM OS CAN CAUSE CRITICAL PROBLEMS IN PHONE AND INSTALLED APPLICATIONS.
IF YOU WANT TO DOWNLOAD A CUSTOM OS, PRESS UP VOLUME KEY,
PRESS DOWN FOR CANCEL.

I didn't do anything yet, my handset is over 3 years old, can anybody suggest me what is the problem ? can I solve it on my own or is it a major problem like motherboard, if it is then I don't think it's worth to get repaired

Welcome to Android Central! You can cancel out of the Download mode, or simply pull the battery -- you won't cause any problems as long as you're not connected via USB to a computer and actively downloading a ROM.

To try to boot into Recovery Mode, it's Power/Vol Up/Home (not Menu): https://forums.androidcentral.com/sa...2-s3-tab2.html. See if you have any success with that.