Bardzo będę wdzieczna za poprawę błędów .
I am writing to apologise for not going your birthday party on Sunday. You can’t imagine had bad I feel. I would write to you to tell you why I didn’t come.
On Sunday morning my sister feel ill. She have terrible stomachache. I must with my sister leave to the doctor. The doctor says that she is ill (grypa żołątkowa) so my sister must stay in the bad at all time. I must with she stay in our home and care for her. That is why I going to your birthday party.
I hope you belive me I tell you how really sorry I am. Please let me to inviting you on a film “Nienarodzony” in the cinema next Sunday evening. Tickets on me. What do you think ??