呢d 英文應該點講????

我買左朱古力做手信
I've bought some chocolates as souvenir (for my friends).
1./ 不可用 a chocolate, 唯一可用 a 的是 a piece of chocolate.
2./ souvenir 前亦不需用 a.

我係倫敦買左盒朱古力比我朋友做手信.
I've bought a box of chocolate in London for my friend as souvenir.

話人地 無誠意/唔夠誠意 應該點講?
Your sincerity are pretty doultful

i buy a chocolate as a souvenir. (呢句有咩問題??)
1)‘I’ 要大寫
2)‘a chocolate’嚴格講係錯，因為chocolate係不可數名詞，唔可以用‘a’
3)時式應該用現在完成式，即‘I’ve bought a box of chocolate as a souvenir of the trip.’

我係倫敦買左盒朱古力比我朋友做手信.(英文應該點寫?)
I’ve bought a box of chocolate as a souvenir of my trip in London.

話人地 無誠意/唔夠誠意 應該點講?
I doubt your sincerity.