Home page, posts and pages appear double

Do you have access or experience with your php files?

Was it always like this or were you editing something when it shifted?

Disable all plugins, does it still happens?
NO? Then enable one by one and find the one causing it.
YES? Then revert to default theme and see if it fixes it.

That should get you started.

No, wasn’t always like that, I can access my PHP files. I edited something in the style.css or header some time ago.

I would double check your front-page.php (or index.php or home.php – whatever you have designated as the front page file for your theme)

You might have accidentally replicated a loop that is repeating /pulling all that information in again? Because it’s even repeating the CSS + script files as well.

You should better reinstall your theme and use a child theme to do the editing.

Make a backup of your database and delete your theme. And reinstall it again. Or use another one, it is not responsive which will do you no good in the search results later on…

@doug: Was a plugin which caused the error.

Thank you all for you help!!!