Category Archive – Hot to remove ?

Hello Hello !

The theme outputs the category like shown below:

Kundenakquise

Here is the image that shows what I would like to change:
https://www.kundenakquisetotal.com/wp-content/uploads/2013/09/category.jpg

I would like to remove it, but I don’t know two things:

1) In which file is the code saved to remove it ?
2) What’s the actual code – how does the syntax look like I have to remove ?

Thank you very much for any little help, I really appreciate it !