If you want to go to Algeria, you should know that you'll need a Visa to enter the country. Here is a list of the countries that need a Visa to enter Algeria: Countries
If you're going to Tromsø, make sure to wear very warm clothes. The weather can be very cold and freezing. Check out the weather in Tromsø by clicking on this link: The weather
Going to Istanbul, you should be careful of scammers. Indeed going to local shops can be very dangerous for foreigners. They will always try to sell you the product for thrice the actual price. Be careful and always negociate the price.
As you know, Machu Picchu is a beautiful place to visit but quite overwhelming. Make sure to stay hydrated and equipped with hiking shoes.
Everyone who has a drone should DEFINITELY bring it while going to the Grand Canyon. You'll have acces to very nice angles to record.
Try to avoid the waiters standing outside restaurants. Usually these places are not the best example of what Athens can offer. Instead do your research and DON'T forget that in Greece dinner is served late.