So from two 2D planes i created a new shape by connecting verticies and deleting edges.
Now i’m left with a shape without verticies (so my UV-map i had on the planes is gone, obviously).
Is there a way to just automatically add verticies or do i have to manually add them (what’s the best way to do that?)
Here’s my example shape
Thanks
No one?
I’ve googled it said “Hold CTRL key and click the left button of your mouse” this did not work though (to add a verticie), but there’s so much outdated info out there (i’m on 2.79b).
It’s ctrl-right mouse after selecting a vert in edit mode, in the latest 2.8. You could just create a plane, select the face, hit x and delete only faces to achieve that example shape.
Thanks Dan! No verts to select if i don’t have any though?
yeah the above was just an example 
It would be pretty unusual to create something by “deleting edges”
more common is using extrusion on edges, and by creating faces manually by selecting 3 or 4 verts and hitting f to make a face from them.
I see, i’ll try that.
But isn’t there a way to put in a vert on a mesh, other than e.g using the knife to cut from one part to the other?
you can duplicate a vert by selecting one vert and hitting shift d enter. or shift d x, moving along x axis and hitting enter. You now have a rogue vert floating in space. if you select two verts and hit f you create an edge. select 3 or 4 and you create a face. usually you select a bunch of edges and hit e to extrude.
sure, you can switch on snap during transform (the little magnet), and set it to face.