607 nightmare

Not long bought a 607 and had nothing but troble with it. Firstly the cylinder head gasket blew. When the head gasket was repaired the car had lost power. I've had a message saying ESP/??? (?= three other letters) system faulty. Starting the car in the morning is a nightmare. as it takes a few seconds to produce any power, there is no acceleration in the car. Any help or advice would mean the world