To my surprise today Jenkins startede to speak to me, that was pretty scary. To change that behaviour then you have to install a locale pluging and set the default language.
INSTALL THE LOCALE PLUGIN
Go to -> Manage Jenkins -> Manage Plugins -> Click on Availables -> Check the “Locale plugin”
Just choose the option “Download now and install after restart”
Go to the plugin manager again and check if it is enabled.
SET THE LOCALE TO ENGLISH
Go to -> Manage Jenkins -> Configure System -> Locale -> set it to en
Check the option Ignore browser preferences otherwise your browser language would set it to your locale and it won’t work.