Microphone in my Blueooth headset is not working

I have bought a new Bluetooth headset, Havit-E500BT. It has a microphone in it which is not working. How can I get it fixed? It’s important for me.
OS: Linux Mint 20.2 cinnamon

Oh ! Another thing.
When I am listening to a video on YouTube, the sound I am hearing is being considered as microphone input. I have noticed this thing. While playing a YouTube video, I opened another tab to perform a voice search on YouTube. I took the words from the video being played.

It could also be that the microphone just listens to the speaker’s output.

Adding the above problem to this one, it could be that your microphone software is set up in a way to only listen to the virtual speaker in the OS. At least, that an explanation of how this can happen, without anything being “broken”, per sé.

No. My loudspeakers were silent when the headset was in use.

Yes. Your hardware speakers. But your software speakers may still work.

If your normal speakers go silent when the headset is connected and yet do not hear anything from the headset speakers, then it could be a general problem with your headset.

Yes, maybe. The speakers inside the headset were speaking, though.

Then consider my initial explanation and check your settings.

I have done everything I can do with settings.