I have bought this new iPhone from another country of mine but I discovered that iTunes Store doesn’t work and also I’m not allowed to download some apps in App Store , I did a lot of researchers but I’ve tried all the stuffs and still doesn’t work

Hello,

Make sure it is set to the correct country for where you live:

Click on the link and read how to "Change your Apple ID country or region" - https://support.apple.com/HT201389

Also make sure you live in a country where there is an iTunes Store:

Availability of Apple Media Services - https://support.apple.com/HT204411 - Learn if you can buy apps, movies, music, books, and more, or use Apple Podcasts or Apple News, in your country or region.