If i stay in front of a closed transparent door there is a hole in the map at the top, left, right and bottom brushface of the func_door brush. I placed a visportal into the door.
Any idea how to fix that?

Why would you place a visportal in a transparent door?

cause the hole gets bigger and bigger if you move the visportal somewhere else.

Since the door is transparent, there is no need for a visportal. Just delete it.

Well, he's not entirely off the mark. A visportal will scale off anything that isn't viewable through it's frame, even if it's open. But if you place it inside a door with a glass screen in it, it will close when the door closes, and that will lead to undesired effects. So, a big nono to put visportals in see through doors.

i also get that bug if the visportal is in front of the door for example 64 units.

If you haven't already, read this and this to get a better understanding what visportals do. This is just a guess as I don't know the geometry layout you are working with but you probably don't need a visportal at all where you are wanting to use it.