i found the fix
first of all see if this is you case:
record a sound and see of your seccound mic is working (wich is at top of your phone) better than the one at bottom or not...
if thats the case i have 2 fix for you both will work XD
1-
go to your app info of "Google" app and seek for permission then turn off the mic permission or deny it
restart your phone and there u go
2-
if you dont have the permission option for google app wich its a case in xiaomi.eu rom
just go ahead and unistall the app updates
restart the phone and enjoy!
3-
if didnt work turn off google assistant (
if u dont use google assistant turn it off anyway its s**t)
whats up with this issue: (for those who want to know)
so yes, new update of google assistant for better resaul want use both of you mic's to hear you better...so it turn your phone mic as mono recording
but our phone seccound mic is not good as the main one so this make the bug
and the reason of the differences between two mic in poco x3 pro is the cheep phone with the big OP hardwere! so they had to make some detail weeker such as seccound mic