Dear *имя друга*,
Good morning! I have bad news for you. I will not go to the cinema with you tomorrow. I'm very sorry! My cat Mandy doesn't eat for 3 days! I think Mandy got sick and I will go with Mandy to vet tomorrow. I think we may go to the cinema next week. For example, Tuesday. 18.00 on Tuesday. I think it is normal time for me and for you.
Best wishes,
*твое имя*