Question: Is there any possibility to deactivate the frontpage (the one with the imageslider) and to just start with the regular site layout?
I already tried to set up a static site or an article in the configuration site of Drupal, but there seems to be a bug, because afterwards this site is no longer viewable (instead of the site the frontpage of the template with the imageslider appears also if the site-URL is entered manually)

Answer: Yes, set up a start page in configurations - site and delete file /sites/all/themes/bluemaster/page--front.tpl.php