O obitelji

Bok, moje ime je Sarah i imam dvadeset četiri godine.
Ja imam mamu, tatu, dva velike braću starija brata, velika stariju sestru i blizankinju.
Imam baku, tri nećaka i dvije nećakinje.

I learn better when someone explains to me why is something wrong, so I will try to explain this to you :) In Croatian, we can write the sentence without Ja, because in we know from the first sentence that you are talking about yourself. So if you continue to write about yourself, you can begin the sentence with the verb and you don't have to write 'Ja'. The second thing - godine, you put e on the end because of the declination of nouns in Croatian. Godina is a feminine noun that ends on a, and by nouns that end on a it goes like this: imam 1 godinu, imam 2,3,4 godine, and if it's more than 4, than you say 5,6,7,8,9,10 godina. The third thing, you say stariji instead of veliki, because stariji refers to the age, and veliki means how big or tall someone is. :) and the last thing, you said baka and nećaci, and that's in Croatian in Nominativ, but you have the verb 'imam' and this verb goes with Akuzativ, but that's the hard part of croatian grammar, I would say. I hope this helped you :)

O obitelji

Bok, moje ime je Sarah i imam dvadeset četiri godine.
Imam mamu, tatu, dva starija brata, stariju sestru i blizankinju. 

Imam baku, tri nećaka i dvije nećakinje.

O obitelji

Bok, moje ime je Sarah i imam dvadeset četiri godine.
Imam mamu, tatu, dva starija brata, jednu stariju sestru i blizankinju.
Imam baku, tri nećaka i dvije nećakinje.

O obitelji

Bok, moja ime je Sarah i imam dvadeset četiri godine.
Ja imam mamu, tatu, dva velika brata, veliku sestru i bliznakinju.
Imam baku, tri nećaka i dvije nećakinje.