BMW 528iA model 98 engine go off while driving!

I bought the car last year on 101 000 km. Now is 112 000. The engine is 6 cylinder 2.8i, M52. It hapens two times. While I drive the car and suddenly the battery and oil pressure lights goes on and the car stops.I am lucky no accident happend because the steering ring became hard and brakes also. After remove the ignition key and wait 15 seconds I start the engine and everything was fine. Also I figure out after bying the car that fuell gauge arrow never goes to max after I full the tank. Also while drive in traffic the arrow goes left and on the highway back to the righ. After I drive 450 km it show me that there is no more km left to drive. But still there is fuel because only 55 liter need to full the tank. Means that there is around 15-20 liter inside. What can be the problem?