Alarmpanel on second Pi with Touch

Hello all,
I’m stuck and thought I’d ask you guys.
What I want:
I have a Pi4 running HA, now I bought the original touchpanel for my second older Pi3 and want to use it only for the alarm.
So the display should only show the alarm panel card (best would be if the Pi automatically updates when changes, Bzw. There is a way to restart this remote via push button).
However, the touch panel should also only turn on and off based on motion, for this I bought the Pi camera and a motion sensor and connected.

I have already tried various alarm panel images (here from the forum) that worked on MQTT. That also worked, but I don’t really like it yet. Also, most of them are no longer maintained.
Theoretically it should be enough if the Pi3 automatically starts on the appropriate homepage (HA).
But I can’t get it to show me only the page without sidebar etc…
Either I have one on top or on the right.
And how do I get the alarm panel to be exactly in the middle of the dashboard? The current set resolution of the display is 1024x768, I find that runs best.

Does anyone of you have something like this running? Or can help me?

Thank you