Connecting Smart 5P Universal Home Phone 4 Plus N 5-wire intercom

Hello everyone, we recently did a renovation and I'm trying to replace the very old intercom handset with a new one.

The old handset is a Thorn handset (unknown model):


The new model is the Cyfral Smart 5P Universal Home Phone 4 Plus N, 4, 5, 6 Wire System.
amazon.de/-/en/Cyfral-Smart-Universal-Phone-System/dp/B07J2ZQPDC


I have tried to use Urmet 1130 as a reference for the wire mapping, as this model looks similar in design to the old handset. The result is that all functions are working (ring, open door, speaking and hearing), but the speaking and hearing volume is really low from both ends of the call.

If someone knows how I can adjust the volume? there is some sort of place for that, but it does not affect the device or I might be using it wrong.

Note: this is an apartment building and I can't replace the building old panel.

Many thanks!

Move the loudspeaker and microphone from the old handset, because, unfortunately, the collective systems have gain control in the "switchboard" and this is set for everyone at the same time (the manufacturer assumes that the subscriber's headphones are identical).