I leave very high up and yet there are many wasps entering. How do I prevent that?
You could install window/door nets. If you can't afford that a curtain should do the trick (with the end of it attached to the bottom frame, so that the draught does not blow it around).
From what you descride you probably have a wasp nest nearby (or there is a vast increase in wasp population in the area but in that case they would be everywhere). Well, you could prevent the wasps from entering if you find and destroy their nest, but unless you are allergic I wouldn't advise you to have it destroyed - wasps are alright to live around with and they won't do anything to you unless you attack them.