I hate this kind of reporting. The German prelates did NOT proclaim that adultery is grave. They denied, beyond reason admittedly, that 2nd marriages don’t constitute adultery. God forbid anyone see such a headline and conclude that the Church says sleeping around when you’re married isn’t grave!
Sleeping around on your first an only, sacramental spouse is adultery.
“Second marriages”, without a declaration of anullment of the first marriage are not marriages, they a license to sin.