in this part of the code
...style="background-image:url(<?php the_field('titelbild2'); ?>);...
You are not inside of the loop so you need to provide the post id. Is this image on an options page? A post? A term? somewhere else?
Assuming that it’s on an options page then it would be the_field('titelbild2', 'option'). If it’s somewhere else the you need to us the correct post id for that location. This is explained here http://www.advancedcustomfields.com/resources/get_field/ under “Get a value from other places”
