You can read the language, it is in the normal 26 letters, but you need a dictionary to understand it. Now I see that you are always sent to the homepage
http://www.gemeentearchief.rotterdam.nl/Hit there stamboomonderzoek. This brings you to another page. Just below the middle of that page is a green area that starts with: Wat vindt u hier? Just below it is the text De Digitale stamboom Click on it. It brings you to a search page.
On that page you can select between dutch and english.
If you really want to do dutch genealogy you need at least a dictionary. Good luck