I've been there many many times

It was going there regularly as part of a USG program and actually had a team of American expats living and working there. I had to get them out in 2011 and 2016 during the Arab spring revolutions. In 2017 I had two get kidnapped on a dirt road on their way home from work in the farm country. They both managed to escape by making a run for it when their capturers were not attentive. Some great times there. I haven't been back since 2018 so I may be a little dated. Based on my trips there I offer the following:

1) Don't be stupid and take chances.
2) First thing to do when you get there is go to a pharmacy and get some Antinal. It is a local anti diarrheal and the best stuff for the local strains. The US OTC stuff is useless. Sort of a Seal Team vs Mall Cops mismatch. If you don't need it that's great. But it is good insurance to have if you get in trouble.
3) Learn how to use a bidet and embrace it! Also bring some Prep H wipes. Chances are your asshole will thank me.
4) My motto there is if ain't cooked, don't eat it. No salads no fruits. Bring some protein/breakfast bars. If you get a touch of King Tut's revenge, go into fasting mode. Eat very little and eat the bars you brought. We used to do a roll call in the morning to assure everyone was FWC. FWC for the uninitiated, is Farting With Confidence. Hopefully you stay on FWC status for your trip.
5) OK now that's out of the way, stuff to see/do. A lot depends on your preferences. I'm not a museum guy, I tend to find them boring. OTOH I find the pyramids fascinating and could sit there and marvel at them for hours. Others see them as a big pile of rocks and what's the big deal. So it's what I find interesting that I'll mention.
6) Giza and the light show at night on the Sphinx worked for me. Depending on where you are staying in Cairo, it can be only 15-20 mins away. Also there are pyramids all over the country. Some off the beaten track are cool. Now as mentioned, a personal tour guide is really a great way to see the city. Your hotel will set you up but you'll pay 3-4x the going rate. If interested, I can reach out to some US embassy/US expats I'm still in touch with and get recommendations.
7) Look into Coptic Cairo where Moses was placed in the Nile and see if that interests. There's a synagogue, Mosque and church there. I'm not religious But I found that very interesting.
8) Look into the Hanging Church to see if that interests you.
9) Look in the City of the Dead to see if that interests you.
10) The Khan el-Khalili (or just say the con) is the old market. I enjoy it. Go at night. You must haggle for everything. Never pay first price. It can be exhausting but I had fun with it at first. After a while the haggling just bored me. US cash rules. Vanilla beans and saffron can be good deals. Just know what you are buying and work them.
11) US women seem to like Egyptian cartouches. I know a guy in the Khan if interested. You need to give them a couple of days to make them and they will bring them you your hotel. Again I'll pass along to info if interested.
12) Nothing to offer on Red Sea diving but I understand it's outstanding. 2-3 of the best places in the world to dive. Watch out for the Russians.
13) The most terrified I've ever been in my life is during a cab ride in Cairo. Seen all types of things there. Just don't encourage your driver to rush.
14)Enjoy and don't be stupid. Don't take chances. Don't dress like an American tourist. Be aware of your surroundings.