Correctly clean filter in draining pipe
The pipe contains a component which I never saw before


Me too


  Is it some kind of filter?


It might be a filter, it might be some kind of device that lets water out but keeps smells in. Though there should be a normal U,S or P trap for that purpose. It could be a type of bottle trap known as an inline trap. It has some similarities to a straight-through pedestal basin trap


  what is the correct procedure to clean it?


No idea but it does look like there are parts which can be unscrewed.



Those collars have ribs which makes them look like they were designed to be rotated by hand. I would start by undoing the metal screw at the very top that holds the funnel to the wall.