i can not find 'German' sound (voiceover) in web. where can i find?
It may have been better to create your own new topic as this one is over three years old and a lot has changed in that time.
I don't think that you will find it on the web, presumably you have the German Language installed (AvastUI > Settings > General) ?
If so then the voiceovers should also have been installed.
But you have to check the option to use Voiceovers, AvastUI > Settings > General > Sounds > Voiceovers.