Samsung tells me that S9 has IP68. Phones are checked before selling and also they are made with all tecnologies that do not allow DUST be inside parts.
I dont know what I should do right now.
Are you able to get to one of our Service Centres so an engineer can have a look at your phone?
I have no idea where might be official service center in Germany near Münster or PLZ 48324.
Have a look at this link to find your nearest store @DmitryMalishev.
I had to file a warranty exchange on my 9 + today because there is dust inside my selfie camera I just bought this phone less than a month ago.