Dear ...(imię do jakiego kolegi skierowany jest list)
I was so sorry to hear that you failed the exam. But don't bother. I really believe that you will pass it another time. The only think that you have to do is consentrate at studying and of course a lot of luck. If you want I can help doing you your homework and I can give you few lessons about every subject you have problem with. So call me if you want.
I wish you a lot of luck, and give me a sign emedietelly after reading that letter.
Kisses (twoje imię)