What exactly do you not understand?

Hello, extension or site does not download mp3 there is no technical possibility.

Hello, how is the name of your browser?

Здравствуйте, сайт или расширение скачивает то что отдаёт Youtube.

Hello, we’d like to help you, but we will need some info about your browser and the installed extension first.
Please, go here http://en.savefrom.net/user.php?info=1,
copy the details that you see and send them back to us.
Please also send us some video links that you can’t download.
Thank you for contacting Savefrom.Net support !

Hello, Yes, we are aware of this issue. And doing our best to fix it ASAP.
Thanks for using our resources.
Best, SaveFrom.net Team

Спасибо что пользуетесь расширением Savefrom.Net

Unfortunately no.

Technically, this is not possible.