Yes, i put "you study" and it wasn't accepted either. So i dont think it was the word "read" that was incorrect, it must have been formulation. But even so, i think "you are reading" and "you read" shpuld both be accepted.
If you're asking "what is the infinitive of this verb", it's kusoma. If it's "what other words for 'study' are there?" you can see them here: https://glosbe.com/en/sw/study - There is no exact equivalent of words from one language to the next.