Hi @blisk1
Try using the phone in [https://www.hardreset.info/devices/huawei/huawei-p30-pro/safe-mode/|safe mode] and check if the microphone now works OK when on a call.
If it does then a ''downloaded'' app ''might'' be the cause of the problem. The trick is to find out which one. You will need to uninstall each ''downloaded'' app, one by one and test the phone in the "normal" mode between each uninstall. When it works OK the last ''downloaded'' app that was uninstalled was the cause of the problem. A ''downloaded'' app is one that you downloaded and installed on the phone and didn't come pre-installed with the phone.