Hello Cocoawildboars,
In a word, you need to adjust the WP setting responsible for the number of posts per page. It is located in Admin Panel > Settings > Reading > Blog pages show at most.
If you are using a 3 column layout, it makes sense to use a number that is divisible by 3. For instance, the demo homepage (which also has a 3-column layout), uses 9 for ‘Blog pages show at most’.
You can find a bit more info about this in the Recommendations section of the User Guide (it’s right at the end).
Kind regards,
Paul