removal of archive header

Dear friends,
A newbie needs help:

I am using the default theme (Kurbick)
When calling from the sidebar categories an archive, a messageline (in German) appears on the top of the display : “Archive for the Category xyz-name”. This line uses bold letters an consumes a lot of the page space. So I should like to remove the line.

Looking at the source code displaid by the browser there ist no hint at where to find the theme and its function to be changed. It says “my domaine/topics/theme..”

I just started to explore the Source code of WordPress and will still need some time to discover the secrets. So kindly apologize that so far I was not able to find even in the support the relevant page.
Certainly I have asked the wrong questions.

Thanking in advance for a solution

knut