Hi @Marius_Berg
I’m a bike mechanic with ~40 years in the industry. Judging by this photo - your rear derailleur is not aligned underneath the rear cog. The camera angle might be deceiving but from this perspective the derailleur is offset to the right, and the derailleur hanger is also bent.
View the top and bottom pulleys of the derailleur together. Draw a centered line between the two, and that line should be vertical. In this photo, that line is substantially tilted off vertical.
Draw another vertical line down the center of the rear cog. When your derailleur is adjusted correctly, the red line should be directly underneath the white one, and both should be vertical.
It looks like the derailleur hanger (the part of the frame circled in red) might be bent. That’s not helping alignment, like building a house on a crooked foundation. A decent bike shop will have a hanger alignment tool to precisely straighten it, and I’d recommend you do that as a first step.
Once the hanger is straight - you can fine-tune the derailleur using these instructions.