Be sure that the radiator is filled to the top and the reservior is 1/2 filled. Warm up the engine and see if the cooling fan is working.If not then turn on the air conditioner and the fan should come on. If not you most likely have a defective fan motor. Your radiator could be plugged up; if so replace it.
Water pump not pumping or a pluged radiater
Yes
There could be many reasons. Not enough coolant or bad flow, faulty thermostat, low oil. If the coolant freezes then it will overheat. If your car continues to overheat then you should have the coolant flushed and thermostat replaced.
One reasons a Subaru Forester may overheat is because the radiator may need replaced. Another reason could be the thermostat.
could be your thermostat is stuck or perhaps and needs to be replaced.
Does that mean that you replaced the thermostat AND the sensor? If not, you really need to replace the thermostat. A sticking thermostat can cause temperature swings and potentially overheat the engine. BTW, BMW engines tend to have serious problems when they overheat. Don't let it overheat or you might be buying a new engine.
because the water pump is not working properly....
Your car will most likely overheat because the water will not circulate properly
The antifreeze level could be low, or the thermostat may need to be replaced, or the antifreeze line might need to be blead to get all the air out, the air in the line will make it overheat.
Most likely
28", I just replaced mine
At the minimum the head will need replaced.