The prime option on Immoscout was a game changer for me when I moved to Düsseldorf. If the owner of the apartment doesn’t pay for prime himself you can only apply for the Appartement after 4 days when it is uploaded. By this time I guess they will have more than 50-100 applicants already. 

Before prime I wrote like 50 applications and got maybe 2 replies which didn’t lead to anything. After I got prime I managed to organize 7 different viewing on the same day in the span of 2 weeks.