Poczatek OK.
My heart started to beat quicklier(FASTER).
I opened the house dorr (THE FRONT DOOR) and went to the kitchen. There I opened the envelope carefully. Inside (THERE) was the (A)postcard from Athens, the (A) letter, and the (TWO?) air tickets (plane tickets??) to Greece!
Dad wrote (THAT) he invited (WAS INVITING - ze zaprasza, nie zaprosil) me and mum to Greece for two weeks!
he was in Athens on a delegation (A BUSINESS TRIP)and he had already managed to sign a (A CONTRACT WHICH WAS) very important to his company.
That's why he got some extra money to buy (THE) ticketS for us.
She was really happy as well as me (Chodzi mi o zdanie "była bardzo szczęśliwa, z resztą tak samo jak ja" ale nie jestem prwna czy as well as tu pasuje??).
SHE WAS REALLY HAPPY, JUST AS I WAS.
We will finally see wiht (BEZ with) dad and we will visit Athens!