And where can I find a supermarket??

Yes, I've also learned by now that simply entering 'supermarket' in Google Maps doesn't necessarily yield the desired results. All the results are several kilometers away, thinking this can't be right, after all, I'm in downtown Cairo.
I chose a detour via ChatGPT and asked what supermarkets exist in Cairo. I entered those names, and now some were shown within walking distance. I went to a small one and was very surprised by the rather limited selection of fruits and vegetables.
It was also kept very simple otherwise; I was pleased to be able to buy oats for my muesli and also a sugar-free cola. I also bought a few spices—rosemary, thyme, basil, oregano—all of which I didn't see. I also didn't see any almonds.

When I went out again later, I saw a similar supermarket. They didn't have any soft drinks at all, just a few small Tetra Paks of juice. There was a larger meat counter. I don't think I saw any cheese and absolutely no fruits or vegetables. There are plenty of those in the streets. It can be a flexible stand or ones that are always in the same place. Some are only there for a few hours, and of course, there are markets as well.
I had asked my roommate about a supermarket. She hadn't found any either. Then a few days later, a new roommate found out that I had been to one and immediately wanted to know where a supermarket was, emphasizing a regular supermarket. This is her fourth time in Egypt. A Chinese guy from the neighboring room saw me frying zucchini and immediately wanted to know where I got that vegetable. I then showed him the street on Google Maps. At that time, he couldn't find one there, but at least onions.
My roommate had a bag from Carrefour and I wanted to know where it was. She said the bag was from Turkey. I just saw on Google Maps that there are actually a few in Cairo. In El Alamein, there was also a so-called hypermarket, something like Walmart on multiple levels. They had a really good selection of fruits and vegetables, a bit more expensive than I'm used to in Cairo. I didn't see any organic products, and a kilo of tomatoes costs 25 pounds here, which is about 42 cents, while in Cairo, it's usually 20 pounds.
I searched for sugar-free cola/Pepsi for a long time but couldn't find any. I also didn't see any hygiene products. I believe they are available in a type of drugstore or pharmacy. They have sunscreen too. I only discovered some feminine pads. I'll ask around about tampons because I'm interested. I don't want to suggest tampons. On the contrary, I've read in various sources in recent years that they unfortunately put cancer-causing substances in them.
The first time I tried to buy oats at a small store around the corner from the hostel, I translated the word 'oats' into Arabic using DeepL and showed it. After totally failing in English on my first attempt, I was repeatedly asked about biscuits? (cookies) In stores, I saw there's all sorts made from oats—cookies, chips..
It wasn't easy either when I tell an eatery no meat. I had that translated with DeepL too and took a screenshot. They usually kindly ask chicken, and I asked a woman in Alexandria as a translation help; she also thought chicken? I feel like I'm transported back to 1994/95 during my first trip to Mexico when I wanted to eat vegetarian, and I was often asked if I didn't want to eat chicken or fish. The explanation that it shouldn't be a dead animal is not always straightforward.
I've eaten fries twice now; I would normally do that maybe once every six months. So far, I've received thin, soft fries. I'm a very big fan of Belgian fries.
I'm really looking forward to flying to Barcelona in two weeks because Amma is coming. I want to buy herbs. I'll also try to find a skirt that isn't so long that I fear tripping, and the prices aren't as outrageous as in the historical quarter. I think I'll also find sandals that suit my taste more easily because I prefer them flat and comfortable.
I had ordered some flip-flops from As Portuguesas right before departure, which I was very satisfied with. Unfortunately, the strap is a bit thicker, and I've rubbed a bloody spot on both of my big toes, so I definitely need an alternative. Unfortunately, one strap on my old ones has torn. I've already glued it with super glue once. But at this point, it's just a matter of time before it's completely unusable.