you need to get your medical done from the medical commision office within 30days.
For a visit visa, you need to do a blodd test, and Xray.
they have 2 sessions, better you go in the afternoon/eveing since the rush is less.
Remember they accept card payment only (QR100)
once your medical is done ,the result would be sent directly to the immigration people.

Your sponsor then needs to go to the immigration office for visa extension.

All the best!