Main slider covers page content

Hello, I have taken over administrating a website for my choir. I've not used wordpress before but so far it went well. However, yesterday for a reason I couldn't yet find out, the main slider suddenly started being displayed over the content of the page that is loaded. Normally, the content would start below the slider. Also, both the slider navigation dots and arrows have also moved up to the top of the page from where they should be. This is the website in question: http://pattu.diskstation.me/wordpress/ The really strange part is, that the page content first in loaded in the correct spot below the slider images, but then moves up to be covered by it. Best regards and thank you for any help Jannis