Unfortunately, you have fallen for a message with a dangerous attachment.

The dangerous attachment at the bottom of the email makes it clear:
"problemloesung.pdf.exe" – there is no reason why an EXE file would be attached here.

The email shown here demonstrates how deceptively genuine fraudulent messages can appear. Carefully check the format of the attachment before opening or saving it.

Further information on how to verify the authenticity of messages can be found here: 
https://secuso.aifb.kit.edu/betr-nachrichten-flyer2