They mix buyers and customers all the time. How can I know which one is meant right now?!
customer can be either 'mteja' or 'mnunuzi'; they both apply
buyer would be 'mnunuzi' since 'mteja' applies to people paying for both/either goods or services. 'Mnunuzi' is specific to goods
Should be fruit and not fruits. Reported on 16.04.2020.
unless the context specifies that the same type of fruit is being referenced, both 'fruit' and 'fruits' are acceptable