This documentation is still a work in progress. For now read "the how to build a flag" documentation to get the best understanding of the underlying architecture.
As of v2.0, the BLE CTF now hosts multiple GATT servers. As the ESP32 can only host one GATT server at a time, you must cycle though GATT servers in order to solve flags and submit flag solutions. Documentation on v2.0 is still a WIP... Stay tuned...