Android and Iphone App Code review/fix needed with GMS / Comm issues

The APP: Very simple APP with problems on MAP Tracking (1 view) and problems to properly handle communications (especially with slow 2G or switching) Mobile APP that currently supports Android from 4.0+ and IPHONE from 7.0+ APP Uses: - GMS (Google Maps) to display maps and locations dynamically - GPS to obtain location of the device that interacts with the MAP - WIFI/Cellular DATA (2G-4G) to communicates to/from Internet - WebService from a central system hosted in the CLOUD Issues: Both Platforms -Maps are not being updated dynamically with the current position of the mobile -We're experiencing Crashes when Internet connection is slow or when switching from Cellular to WIFI Android: -We're noticing GMS local DB locks and errors logged at the phone (on Android) -Push notifications are not working What do We need?: Somebody with proven experience on Mobile development with master knowledge on working with MAPS and GPS. That provides expert code to properly handle GMS and Communications in a way that makes the APP more reliable. The professional we'll hire should be a fast worker to be able to deliver corrections in a short time. We don't want to redesign or rewrite all the code, just to fix the parts that are not working. We're open to receive propossals on how to better tackle this. And the best approach will be the one we will consider for hiring. Newbies please DO NOT apply.