[GAN-BATTE]

It means 'Go for it! / Do your best! / Keep it up! / Hang in there! / Give it a try! / Good luck!' in Japanese. When you cheer your friend up, you can say it. If you add 'KUDASAI' at the end, it would be polite. Also, you can say 'GAN-BARE' to your friends as same as 'GAN-BATTE'. But you can't add 'KUDASAI' at the end of 'GAN-BARE', it can't be formal.

'I'll do my best' = Gan-baru(casual) / Gan-bari-masu(formal)