Hello,
There is a password to my website and i want to create a riddle that appear in the landing page so the visitors must resolve this riddle to enter to my website.
Is there a possibility to change this home page ?
That isn’t your home page, that is just the Wix Custom signup/login form.
https://support.wix.com/en/article/about-the-member-signup-form
If you are not wanting to use either the Wix own window or the custom Wix window, then simply make up your own custom login and signup lightboxes for your site.
https://support.wix.com/en/article/corvid-tutorial-creating-a-custom-registration-form-with-code
You can add whatever you want to your home page itself.
https://support.wix.com/en/article/changing-your-sites-home-page