Nico, SmartLynx is an ACMI Airline, which means they provide services for other airlines.
Right now SmartLynx has a contract with Air Peace from Nigeria, which means they are operating flights on behalf of Air Peace, so yes, you can be rostered to fly in Nigeria. I don't know exactly how long is each rotation (I suppose it should be a few weeks stationed there).
Just go in FlightRadar24 and you'll some A320 from SmartLynx operating Air Peace flights in Nigeria.