Spoken or written language?

If I want to learn Swahili, is it enough to learn just the spoken? Or should I also learn the written? Is written Swahili difficult?

It depends on how you want to use the language.

Jambo!

Written swahili is not difficult at all. All you'll have to learn is how to pronounce words the right way.

Fun Fact: Swahili was written at first using arabic script but the arrival of precolonial christian missionaries changed it to the roman(?)