Hey Bastian.
Firstly I wanna say thanks for including our entry in your review video on youtube! It was so great to watch someone else play and see what you liked and didn't like in real time!
Secondly, I'm going to tell you what you missed on the lake level and I think you're gunna kick yourself. On level 1 & 2 when you placed the statue on the glowing mark it locked into place. But on level 3 the first statue did not lock after you placed it on the yellow fish. Once the bridge is raised you have access to the second yellow fish and you can push the first statue onto it and then it locks and raises the bridge that gives you access to the glowing blue mark! The link is that the one statue is responsible for both yellow marks ;-)
KBoss did a full walkthrough of the Night Keeper if you want to see what I mean or check out what you missed in the remaining 2 levels. But I'd love it if you went back and gave it another try 😂