The thing is it would be weird to translate them, because they are items that really doesn't exist in western cultures. You could just translate them as "cloths," but that's inaccurate because a lot of things are cloths that aren't kitenge or kanga. They are a very specific type of cloth. You could translate kitenge as Dashiki, but I feel like even that's inaccurate because while dashiki shares the same design as many kitenge, kitenge can have a lot of different designs, and I'm not even super positive that dashiki are the same cloth, because I've felt many that certainly don't feel like kitenge.
I don't think there is really a way to "fix" it, Duolingo users just need to do a bit of exploring and cultural studies to learn what kanga and kitenge are.