As written in the topic above, my Huawei P20 Lite can only make calls with the speaker switched on, so I will only be heard when I switch this speaker on. Hearing is also possible without a loudspeaker.
Seems to come more often?! With the cell phones.
Solution?
A reset to factory settings did nothing.
Make a voice recording with the Huawei recorder, if nothing is recorded then the microphone is broken or has a loose contact if it only occurs once.
Where is the recorder from Huawei, I have many recorders as an app on a mobile phone
Then take any one, recorder is recorder