concrete5 is a database driven CMS which will not store the actual pages on the server but instead store all content in a database. The themes and templates used by concrete5 can be considered the front-end holding your chosen blocks, which in turn pulls their content from the database.

Now that being said I think I can help you with translating just the guestbook block (instead of your whole installation).

There are several ways you can do this, but the one below I think will be the best for you:

Create a custom template:
Custom templates are just that - custom. You can apply a custom template to a block to render a different view of the block without ever touching the underlying functions of the block. In your case that would be translating all text into Dutch.
The first thing you need to do is to copy view.php and view.css from 'webroot/concrete/blocks/guestbook' to 'webroot/blocks/guestbook/templates/dutch'. You will have to create the directories yourself.

Now open up view.php from 'webroot/blocks/guestbook/templates/dutch' in a simple text editor with utf-8 encoding. You will now see the code used to render the view of the guestbook. To translate from English to Dutch you need to change the wordings inside the echo statements like below:

From:

into:


Continue with all echo statements and you should be good. Now I don't know Dutch (translation above from Google Translate) so I can't help you with the actual translation.

Once you have changed all echo statements you need to save the file and make sure it is saved in 'webroot/blocks/guestbook/templates/dutch' where you also have a file named view.css (copied before, if you remember).

To apply your translation you need to login to your site and edit your guestbook block. Click on your block and choose 'Custom Template'. In the dropdown list you should now be able to select a template called 'Dutch', which was what you named your template folder above.

I hope this helps.

Good luck!