Approach to load testing a Geolocation iOS app

I created an iOS app in Swift, and utilized Firebase Auth and DB for the backend. I can't get super detailed on the specifics, but it involves Geolocation services, and is similar (although much simpler) to Uber/Lyft. Both drivers/riders share the same app. You have to click on a another button to get to the driver interface.

I need to create a simulation where multiple virtual users (both drivers/riders) are using the application at the same time (I would like to measure success/failure of each action, as well as response time). I don't need to randomize the simulation, but I do have to account for the fact that there is an interaction between two users. In other words, it's not the usual performance test where you log-in, view profile, update profile, log-out, etc. There is a dependence on one part of the test to complete before the other can start.

I'd like to see if I could get any ideas on the best approach to handle this. I can provide more details/context, if needed.