Additional meeting and call-related features and issues within Microsoft Teams for Education
Hello S Panayi,
Welcome.
Please press Windows key + R to open the Run dialog box, then type "mmsys.cpl" > click Recording tab in the Sound window > select the used microphone, then click Properties button > in the Properties page, click Level tab> manually set to 50 > click Advanced tab > uncheck the Allow applications to take exclusive control of this device option under Exclusive Mode section.
Feel free to let us know how it goes, and take care.
Regards,
Rudy