By the way to be sincere, I've interacted with Tanzanians on several occasions, though they use Swahili most of the time, but very few speak it fluently, try check this out if you've studied Swahili literature, especially the ones from Coastal region. Most from other regions like Mwanza are good in the language, but the Coastal guys only tend to add some flavor in the language flow but do speak very broken Swahili.