deb http://ftp.de.debian.org/debian/ testing main
deb-src http://ftp.de.debian.org/debian/ testing main
 
deb http://security.debian.org/debian-security testing/updates main contrib
deb-src http://security.debian.org/debian-security testing/updates main contr$
 
deb http://http.kali.org/kali kali-rolling main contrib non-free

nano /etc/apt/preferences.d/debiankali
Package: *
Pin: release a=testing
Pin-Priority: 1000
 
Package: *
Pin: release n=kali-rolling
Pin-Priority: 800

wget -q -O - https://archive.kali.org/archive-key.asc | apt-key add
apt-get update

deb http://repo.vivaldi.com/stable/deb/ stable main
wget -O - http://repo.vivaldi.com/stable/linux_signing_key.pub | apt-key add