Hi together, thank you for the good replies. As I am also a collector of european swords I am fimilar wird layer pattern in steel, but the structure on this tanto seems to be different, thats why I am asking here.
I added another picture where one can see that these lines are harder areas that stand out from (some long time ago) polishing.
It could be something with different steels but I also have such blades like Sansei was showing and they look pretty different to me.