Yes, you can see the deltc right there in the bottom right of the image.
I have generally not needed to adjust often. I have the bike for 1 year now.
But, I do remember it was only the screw underneath I adjusted, but this no longer works.

This now, coupled with other issues I had (having to adjust brakes and index speeds a couple of times, with like only 1500km, and chain being REALLY prone to rust), makes me feel I have been duped. My cheaper old chinese ebike did not require 10% of the maintenance :/

Would you be able to give more specific advice if I posted a photo from the inside?
Also, what is the name of the hinge? I imagine with a name I could maybe find a manual.