Idioms

 WHEN YOU SUPPORT SOMEONE 

TO HAVE SOMEONE'S BACK - to support/protect someone (підтримувати, захищати) 

Don't worry, I've got your back.

TO BACK SOMEONE UP - to support (підтримувати)

 I really need you to back me up!

TO STICK UP FOR SOMEONE (phrasal verb)-  to support or defend someone or something, especially when a person/thing is being criticized (підтримувати, заступатися за когось чи за щось, що критикують)

Stick up for what you belive!

TO STAND BY SOMEONE (phrasal verb) - to support, be with someone (продовжувати підтримувати когось, хто у важкій ситуації)

TO STAND SIDE BY SIDE WITH SOMEONE- Support (підтримувати)
  I promise, I will stand side by side with you. 

TO GIVE/LEND A (HELPING) HAND - to help/support someone (допомагати, підтримувати)

My sister gave me a helping hand.