YOU SAID:

my friend's girlfriend is cheating on him with 3 people. one of those 3 is me. she gives me kisses

INTO JAPANESE

友達の彼女が3人で浮気してます。その3人のうちの1人が私です。彼女は私にキスをしてくれる

BACK INTO ENGLISH

My friend's girlfriend is having an affair with three people. I am one of those three. she kisses me

INTO JAPANESE

友達の彼女が3人と不倫してます。私もその3人のうちの1人です。彼女は私にキスする

BACK INTO ENGLISH

My friend's girlfriend is having an affair with three people. I am one of those three. she kisses me