Before you change country make sure you have downloaded and backed up any purchases from your previous country's store. You will not, in most cases, be able to re-download them again once you change countries and it won't be easy to change countries to the previous one once you lose your payment method for the former country (as well as a wait period). As long as you have them on your computer you will be okay.
Read this Feb. 2018 post by Dah.veed post regarding possibly still having access to some apps if they are in the stores of both countries - https://discussions.apple.com/thread/8289669?answerId=33055125022#33055125022
Change your iTunes Store country or region - https://support.apple.com/HT201389 - In small, faint print, "You might not be able to redownload some of your purchases from your original country or region." This may also mean any subscription services you use may no longer work (e.g., Apple Music).