Temperature staying at half is actually good. That's the recommended temperature. Most of the people including myself here are using 'thermostat valve' and automatic fans, that keeps the temperature at half all the time. Maybe your car has that thermostat valve installed. If its already having that, do not remove it.
If its missing, get a 82C new valve and install it. Get good quality coolant too, water will rust the engine internally causing irreparable damages to cylinder head and block. Get 90-92C automatic fan switch too.
Other than that, get the water pump checked, maybe its fins are rusted and its not circulating enough coolant.