Oh and of course I’ve added the `<?php previous_posts_link(); ?>
<?php next_posts_link(); ?>` links.
I think you can not navigate to another page by using the next_posts link or even the next_post link; they are for posts, not pages.
Posts are written into category’s and when I understand correctly what you want, that is done easier by writing posts and putting them into appropriate categories.
Because of your prmalink setting I cannot see if “Nouvelles” is a category. If it is, then you limit the number of posts to 5 in the admin panel/read settings.
Next in your category or archive.php use the postS links you mentioned.
Next, clicking on a posts title brings you to that full single post. The way it looks is generated by single.php
To navigate to next or previous full post within “Nouvelles” use next_post (without the S) etc
<?php next_post_link(' %link', 'Nieuwer bericht »', TRUE); ?>
the TRUE lets you stay within the category.