Ranking German Language Site

The site is gray niche, but totally legal. DR is 50. 8 years old. It's a multilanguage site and the German version is currently ranking 20-50 in Google.de for about 20 kwds I'm interested in. I need to get 10 of them in the top 10. I am NOT interested in German language keyword links from English language pages/sites. Source page/site must be German. I've tried quality crowd links and got a little boost, but it soon faded. Also, I researched Reddit and Quora and they are not big in Germany. I don't want any anchors to include keywords (generic anchors only). So the keywords must be on the page elsewhere, or the page must have relevant LSI. Interested in niche edits (with guaranteed longevity), guest posts and even quality PBNs. But will not even consider junk links with toxic potential. This is an established quality site and I don't plan on trashing it. If you think you can help, PM or leave a note below.