Gap on top and side of entry door
It looks like your door is warping. There's probably no way to fix the door itself, but there are a couple of things to do that can help.


apply or move the weatherstripping so that there's no air passing through
re-hang the door to split the difference of the warp between the top and bottom. This will never be a perfect solution, but it's done pretty regularly.


You should ensure that the door has been painted on the top and bottom edges, as this is one cause of warping. Also, you should make sure that moisture isn't being dumped onto the top of the door from the outside.

There's also the question of what warranty obligations the builder has to you. You'll need to consult locally, but they might be legally required to fix this. (And, in my opinion, a fix would be a new door. However, standards of what is acceptable vary from place to place.)