Thank you for replying, and don't worry about being unable to help.
I know that we should upgrade the website, but it is a bit tricky as it is manage by a subcontractor - which results in higher costs for our ngos. I was thus first trying to see if I could somehow solve the issue with my small understanding of joomla!
But now upgrading the website will definitely be on the to-do list.
Thanks and have a nice day,