Ok…I deactivated all active plugins, and now the layerslider are up and running again… :) So that worked super!
Now…Which plugins do i need for running the site?

yup…here goes:

http://www.subevent.se/photo_ver3

Thanks a ton!! :)
Now I´m updated and all is well…except that the slider shows a red message instead of the slider.

Layerslider: Old jQuery issue
It looks like you are using an old version (1.10.2) of the jQuery library. LayerSlider requires at least version 1.7.0 or newer. If you are using the WordPress version of LayerSlider, you can try out the “jQuery Updater” plugin from the WP plugin depository. If you don’t know what to do, you can write us a private message from our CodeCanyon profile page. We need a temporary WP admin account (or a temporary FTP account in some cases) to solve this issue.

any suggestions?

…thanks Yigit
but which is the easiest way to update from my current version…? (its 1.9 something…)

Where? …where do you find these “settings”?? I can´t find anything inside wordpress allowing me to update the theme…!