OpenStreetMap

We need some advice about the map services provider. We are a mobility app that just launched 5 months ago in Tunisia offering P2P carpooling. We are currently using Google Maps API for maps (Places API, Geocoding API, Directions API & Distance Matrix API). Thus, we received expensive bills from Google Cloud following the number of requests we are using. We are looking forward to reduce the number of requests in general because we can't afford these large bills at this stage, knowing that they are going to increase proportionally to the active users of the app. We tried to optimize multiple times but it isn't enough. We are searching for optimization advice or ideas on how we use the APIs, or other map providers (like OpenStreetMap or similar) that offers free or cheaper options than Google Maps, without lacking quality of information (we are in Tunisia and we have to choose options that have enough data about Tunisia). Thanks!

Which will give a better map (better view, markers options, info window) in an Android OS app?

Leaflet with Mapbox or Leaflet with OpenStreetMap?

I use OpenStreetMap because that has a strong community. It takes some time to catch up with Google Maps, but OpenStreetMap will become great solution.

I use OpenStreetMap because i have the control of the environment, using Docker containers or bare-metal servers.