What are the best KPIs for a mobile Navigation app?

We are working on a map application. Something like a simplified version of google map for local people. It allows users to search for points of interests as well as a turn by turn navigation for car drivers.

What metrics do you think would be good to measure as KPIs?

We are tracking Monthly/Daily Active Users and Time in-app with fabric and numbers are growing steadily but how can we get an idea if we are doing good or not?