Installation with dimmable TL lights

This is my first time installing a shelly and now i am wondering if i understood it all wrong and bought the wrong device for the job.

In a bedroom we have T5 TL lamps op top of a wardrobe. those are dimmable.

There are simple impulse wall switches at the moment. Just a short push switches on and off the lights in their previous state of brightness. A longer press dims up or down.

There are now two wall switches that do the same thing for these fluorescent lights.

Now i wanted to add a shelly to be able to add a remote button.

I thought for dimming i need the dimmer 2, but now i am starting to think that maybe it is not needed because i think the dimming is done by those eltako's in the electric cabinet ?

I installed it as you can see in the photos attached.

When i start calibration it dims up or down but then stops and says it fails. Also not sure what settings i should use for this setup.

Thanks for any feedback ..