ᐅ Water streak on exterior wall

Hello everyone,
Are you familiar with water stains on walls? They only appear after it rains.
This concerns a house that is about 4 years old.
Do you know if this indicates a defect? Should the wall be repaired in some way?
I’m quite uncertain about the stain.
Do you have any other ideas about what it might be?
Best regards,
Sebastian

It looks to me like the water is running down from the sheets at the top.
What type of roof do you have? What does the construction look like up there?

Hello Jochen,
thank you for the quick reply.
The house has a flat roof with a slight pitch.
From the outside, it looks like this:

I have never been up there.

Good luck, Jipeng

Are the "water marks" on the side or at the back (lower side of the roof)?
Did they appear only yesterday and the day before (storm), or also during "normal" rain?

Hello

There is not much to see in the pictures.
A top-down photo would be necessary to understand the construction and installation of the cover.

Olli

In the pictures, it looks like the water runs down from the metal sheet on top and not underneath. Due to the slope, the water probably follows a common path.