Recommendations by city:

Lima:

• Lima is enough for one day, but it would be better to spend 2 days going to Ica to visit the Oasis Huacachina, which is only 4 hours away from Lima.
• If you're looking for a nice restaurant, I can recommend "Central" and "Maido" in Lima, but you should make a reservation about 3 weeks in advance, they are really top-notch in Lima.
• Directly to Huacachina takes a maximum of 4 hours if you drive slowly. In one day, you can see almost everything: Larcomar, Miraflores, and Barranco are particularly beautiful.

Ica:

• Local dishes such as Arroz Verde with Papa a la Huancaina, Carapulcra, Sopa Seca, Ceviche, Pescado Frito, and Tamales are recommended.

Iquitos:

• It would be better to spend 7 days in Iquitos, as there are more things to do and see there.
• In Iquitos, there is an island restaurant called "Al Frío y al Fuego", which is super nice and located right in the city.
• Be careful in Iquitos, there are many offers to try Ayahuasca, from fake shamans who may also sell banned substances, and then they could steal from you. This is also done by Europeans living in Iquitos.

Cusco:

• It would be better to spend 5 days in Cusco.
• In Cusco, the "La Cuzqueñita Restaurant" is very nice and there are traditional events. It's better to go there on Fridays or Saturdays.
• Recommended dishes are Cuy Chactado and Pachamanca.

General recommendations:

• If you want to travel from Cusco to Iquitos, you will have to return to Lima, which means longer travel times and higher costs.
• The bus ride from Lima to Cusco can take a long time, and if you suffer from altitude sickness, it is advisable to stay one day in Arequipa to see if your body will tolerate Cusco or not. Arequipa is on the way to Cusco.
• Traveling by bus in Peru is cheaper and more comfortable, but if you buy plane tickets 2 months before your trip, it will be cheaper.
• You can buy a SIM card at the airport, but it is very expensive. I recommend doing this in Miraflores instead. It is also advisable to book a hotel there.
• There is also direct transportation from the airport to Miraflores. Taxis in Peru do not have a meter, so they will ask you for a lot of money, even in euros or dollars.
• I had no problems with a SIM card in Peru, but generally, you can have Claro, Movistar, Bitel, and Entel.