Jakoś koślawo przetłumaczone... więc ja poprawie:
I write to you because i need to tell you about my illness I experienced yesterday
Well..I rode by bike to my friend and went together on trip. In the end of the trip it started raining. we were wet.We rode really quickly to home. after two hours I felt really bad, I had fever. My mum told me that I had to lie in bed. I felt pain in my muscles... I couldn't even move, it hurt so much.
That's why I couldn't go with you to the cinema.