why my temperature gauge does not go to the half wat mark ?

Hello, this could be totally reasonable and normal - it's too hard to say without monitoring the actual temperature reading from the engine coolant temperature sensor reading for one thing, and getting a sense perhaps of the actual coolant temperature with a thermal heat measuring thermometer. If it is found that the engine is not getting to proper temperature, it could be that the engine thermostat is staying slightly open, or sticking open too long. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops