"Bandari ya Dar es salaam ni kubwa"

Translation: The harbor of Dar es Salaam is big

[Mrsaiz]

Maybe "Salaam" shall be capitalized?

[gloucester5]

Port and harbour both translate as 'bandari' therefore both options should be accepted answers.

[gloucester5]

There is also an English grammar issue: the harbour 'of' Dar es Salaam is incorrect in English - we would always say 'in', or more accurately, 'Dar es Salaam harbour', without a preposition at all.