Thank you sonele, that was an issue.
Now I have solid ~72.8 MiB/s without a hassle
If its fine for everybody, I would like to write small instruction in my original post, for those with same issue as me.
How I did it ?
First Get your IP of Android
in my case Pixel 6a with GrapheneOS.
In phone Settings>Network&internet>Internet(WiFi) find your wireless network.
look for Settings Icon, next to name of your network.
Inside Look for “IP Address” and write it down (mine is 192.168.1.56)Get your IP On Qubes
Network Icon>Right click>Connection Information
Look for “IP Address” and write it down (mine is 192.168.1.209)Syncthing on PC .
Remote Devices:
{your-device-name}>Edit>Advanced Tab
In Addresses field, removed name “dynamic” and put your android IP tcp://192.168.1.56Syncthing on Android
Tab Devices>{your-device-name}>find field from the top with written “dynamic” inside remove
and put instead Qubes IP tcp://192.168.1.209That should do it.