Bardzo proszę o sprawdzenie

Zadanie polega na napisaniu listu do kolegi, który zaprosił nas na urodziny, ale musimy mu odmówić.

Thanks for your invitation. I was really happy when I getting that. Unfortunately, I can't going on your birthday party. I'm sorry, I was have to visiting my grandmother in a hospital. Because I don't saw her for ages and this is really emergency. Oh, on Monday I bought a small present for you. Maybe tommorow, at 18.00 pm will we be coming together in central park? I want gave you this present. So, see you tommorow!
PS I wish you succesful party of course!

I was really happy when I 'getting' (zmien, to jest zle slowo) that.
Unfortunately, I can't 'going' (zle slowo) 'on' (znowu ta kalka z polskiego 'na' kiedy to sie skonczy, tutaj ma byc inne slowo) your birthday party. I'm sorry, I 'was' (niepotr) have to 'visiting' (zle slowo) my grandmother in a hospital. Because I 'don't' HAVEN'T 'saw' SEEN her for ages and this is (tu cos brakuje) 'really' (zla czesc zdania) emergency.
Maybe tommorow, at '18.00 pm' (niema czegos takiego, jest 1800 hours, albo 6p.m.) will we 'be' (niepotr) 'coming' (zle slowo) together in Central Park? I want TO 'gave' (czas teraz) you this present.
I wish you (tu cos brakuje) succesful party of course!