Is my X5 overheating?
 

According to readings of the coolant temperature on the cluster display (system test nr. 7) the engine temperature is regularily between 110-113 degC (230-235 degF). This seems a bit high. Though the regular engine temperature gauge meter usually shows a normal reading. The car is a 2002 4.4 X5.

Is this normal? If not what could be the possible cause?

For info the car is operated in an environment where the ambient temperature always is in the range of 30-34 degC (86-94 degF).

Further there appears to be a coolant leak. If I top up the expansion tank to the maximum mark the level will drop quite quickly with about 4-5 dl (2 cups), however after that it appears not to drop anymore.

IIRC, V8 runs warmer than I6. The temp range 86-94F is for I6. If you have coolant leak, you need to inspect and fix it. BMW cooling system is pressurized, so it's best to have it leak-free. How many miles (km) are on your X5? Preventative cooling system overhaul is around 100K mi (160K km)

On the clock this car has 93K m (150K km). What is typically needed to be done during the preventative cooling system overhaul?

expansion tank, hoses, thermostat, water pump, seprentine belts and pulleys, maybe the radiator too.