Dust under lens, and microphone noise

Hello,

I have two problems with my iphone Xs:

I have dust under the lens, i cleaned it from the inside several times but it always come back, even with a waterproof seal. I don’t know where does it come from, maybe the flash cover? There is more dust under the main camera (on the top). Do you think replacing the lens cover will help?

I have a problem with the rear microphone, here is a vidéo :Youtube . There is some loud noise every time I record a vidéo, and especially when I stop it. I replaced the flash flex cable but this problem stayed. Does I need to glue it in place?

Thank you for your help.