Hi this is your home page id
http://www.polderij.nl/?page_id=19
Now you can see the home page id also.
All the latest post will be displayed in the home page. This is your domain name http://www.polderij.nl/
and this domain name cannot be changed. So on the index page you will see http://www.polderij.nl
and if you assign a front page display (home page) then it will display http://www.polderij.nl
instead of displaying http://www.polderij.nl/?page_id=19
Hope you got me what i mean to say.
I didn’t find any issue in your site too.
Thank you