Yes, you really can’t just overlook that from the ground floor. Especially since the big earthen mound in our garden won’t be staying there. We will level it and then have grass there. And our focal point, basically where everything is oriented towards, is naturally exactly that corner with the metal shed, because that’s where our garden is largest.
We can make sure on our property that we set up some privacy screening so we don’t have to see it anymore. What annoys me more is the broken agreement we had regarding the hedge. We were a bit harshly presented with a fait accompli there, but I’m not going to start any trouble over the garden with people we’ll have to get along with for the next 20 years. It’s not that important to me. I just want things to look nice on my side, and we’ll manage that somehow.
Currently, I’m thinking of fence elements like these:

And I would then green them on our side, and the neighbor can do and put whatever he wants on his side. :)