Clone geolocation app admin and backend

We would like to You to develeop/clone geolocation app admin and backend or our geospatial learning app (almost like city guide together with quiz).

We would like You to develop next version of this half-developed app, which would work better. Backend is hosted at back4app, we would like to have an independent backend in new version.

Functionality of the current admin-site is described in the help file, which is attached. App functionality is also in help file.

Can You:
1) Develop/clone admin site to do the same as the current backend
2) Make our app work with your backend. We have app source code.

There are some changes, which need to be done to the backend. These changes are
outlined in the attached file.

How much time would You need to do the above? How much would it cost?

We are a NGO with low buget, so we prefer reasonably priced developers.