Problem fix update...tray

sudo add-apt-repository ppa:nilarimogard/webupd8 ; sudo apt-get update ; sudo apt-get install -y launchpad-getkeys ; sudo launchpad-getkeys

problem fix update...tray this

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apt-key update

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gpg --keyserver wwwkeys.eu.pgp.net --recv-keys 9AA38DCD55BE302B
apt-key add /root/.gnupg/pubring.gpg
apt-get update

or do this

apt-get install debian-archive-keyring