Minecraft why?

Why am I at the edge of the map and not so in the middle?

Because the cards are not created according to the player position in the middle, but according to chunk positions or regions…

And how do I make sure that the map is created in the middle?

By going to the center of the map and building there. There's no other way. The map is permanently assigned to the region in position… You can't move the view. You can only create maps around it and merge the maps so that you get a large map in which you are reasonably centered…

Why do you want to create the map in the middle, you don't care

But that the rear things are also shown to me on the map.

Oh, unfortunately you can't influence that. However, as soon as the arrow is no longer on the map, you can create a new one and hang them up next to each other in item frames, for example. The link shows you how. (It's a bit old but still works)