Rewrite an existing app on iOS and Android

WE HAVE DECIDED WHOM WE WANT TO WORK WITH, SO PLEASE DON'T SEND ANY MORE OFFERS!!!

I have done an app a few years ago. Now the app stopped working on the actual iOS. There are some synchronisation issues and some ui issues (maps are not showing correctly etc.).
I'm looking for a partner who's interested in overhauling the app. It should be totally rewritten for Android and iOS.

Here's more info on the project:

the app is on iOS currently programmed in Objective-C.
The app is called "NÖ4Kids". It's an app that's offering guided tours in our city for young people.
Here's the link: https://itunes.apple.com/at/app/no4kids/id652215877?mt=8
I have written synchronisation scripts which synchronize the data between the web server and the app. They're all JSON based.
Within the app everything is saved in a data model with 6 entities in total.
There's also a web-app which offers nearly the same functionality:
http://www.noemedia-app.at

WE HAVE DECIDED WHOM WE WANT TO WORK WITH, SO PLEASE DON'T SEND ANY MORE OFFERS!!!
Thanks and see you soon
Bernie