Multiple languages

have an app called iFoodie. It promotes restaurants worldwide on Apple app store and Google play store. My website is www.ifoodieapp.com. I have started working on LOCALIZATION aspect. With the app so complex, I am dealing with issues. I am wanting to add restaurants worldwide in my app daily. The thing is that my goal is to have plethora of restaurants, and each day I will add more restaurants. Also, this is important. My case is TOTALLY different. I want to type in the BACK END in ENGLISH. But, it will show up on the app in different LANGUAGES. Like, if the user is in SPAIN. He or She will see the content in Spanish. Like, if the user is in RUSSIA. He or She will see the content in RUSSIAN. I know either Google or Apple will take care of that, when user downloads the app. App is smart as to know (feel), the phones GPS. Hence, it will download the appropriate LANGUAGE. But, I still don’t know. Please help figure out my issue. Also, does my app have to be in multiple appstores, since it is trying to cater to every foodie? And help restaurant find a way to advertise.