Please, any recommendations to visit in Cairo?
The obvious answer is the pyramids and the Egyptian Museum followed by Islamic Cairo and perhaps Old (Coptic) Cairo but more detailed replies would depend on you detailing a little something of your interests and preferences.
Pyramids, museum and big bazzar. If yiu have enough days to spend then add memphis and old Cairo
Definitely also the Citadel.
I suggest that you read a guide book and see what appeals to you as how you choose to spend your time depends very much on your interests - which you have not mentioned.
I did a lot of background reading before my first visit to Egypt and, with only 3 whole days in Cairo that occasion, I spent one at Saqqara after a brief detour to Memphis, one at the Antiquities Museum and one at the Giza Pyramids and Solar Boat museum there.