How did trade affect the culture of east african city states?

Brings in revenue, business, and people. Those that they trade with/do biz with spend money there and also visit to make sure everything's all right. Basically, any country/city/state that has any sort of trade to market to others, it will only bring more money to the people.

The only thing you need to worry about is being fed way too much food and being introduced to all the family members, relatives, and neighbors, who will keep you for a never-ending conversation because they want to make sure you get the best hospitality.