@AppLee @mardy Halleluja, this was exactly what I've been searching for.
The bug-report already exists and we can only wait and hope that it will be solved soon.
Thank you and have a good day!

Hello and thank you for the post! I'm running a private matrix server for my family chat and unfortunately Cinny isn't able to handle this (no logon possible). So I'm still on FluffyChat and I hope that you will still support it. Up to now I haven't activated Pantalaimon but a full integration into the app would be fantastic. Please keep up your good work!

@AppLee @mardy Halleluja, this was exactly what I've been searching for.
The bug-report already exists and we can only wait and hope that it will be solved soon.
Thank you and have a good day!

@applee Thank you for your hints. Even though I'm one UT nearly from the start (BQ Aquaris E10, Nexus 5...) I've never searched for help in this forum. I'm still learning...
So if you think it would be best, please close this thread and I'll open up a new one. Wich category do you think, suits best for this case?

@applee The behaviour on Androids side is as it should be. As I said, my daughter switched back to Lineage and all these problems were gone. I already tried uVolMan but it seems that the volume of the speaker when calling somebody cannot be put up to maximum as for example when listening to music. The volume shows maximum but is still very low. And it cannot be pushed further up by uVolMan.
If I say the volume is low, it means that even in a total quiet environment you have to listen very concentrated to hear the person on the other side talking. I often talk with my children with my wife beside me and on a "normal" smartphone this is comfortably possible. With my RN7 is isn't really a good option.

@AppLee Thank you for your answer. I will try to do so and see if it gets better. Still this leads directly to next obstacle: the volume level of the loudspeakers is very low (in telephone calls) and I cannot turn it louder. You always need a quiet room otherwise you wouldn't understand the person on the other side. Maybe these two problems are linked with each other.

@whitemagik Hello Friends, I'm using a Redmi Note 7 too and I'm experiencing the same problems. I'm on OTA-20 and the echoing persists. My daughter had another RN7 with the same problem and she had to switch back to Lineage due to this annoying effect. Every help would be greatly appreciated.

@josele13 Thank you for your answer! I was already on RC but I switched back to stable (OTA 20) just to test it, but no sucess. If I call somebody and put the speaker on, the other person always hears his voice double.

I can confirm this issue. This echo happens on every RN7 I tried so far. Unfortunately always using headphones isn't really an option for me. Has anyone found any other solution for this?