How to fully switch Prestashop 1.5 to ssl

[rethus]

How can I switch Prestashop 1.5 fully to https?

I use it as multishop and installed an SSL-Certificate for the domains.
But some Content is still http based. Even like the Link into the cart.

Is there an tutorial how to switch the whole 1.5 to https?

For sure, I could force it via htaccess like this:

RewriteEngine on
RewriteCond %{HTTP_HOST} ^myDomain.de
RewriteCond %{HTTPS} !=on
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

But isn't there a clean way to change all internal page-links to https?

Edited October 10, 2018 by rethus (see edit history)

[rethus]

Ok, solved it. The SSL-Flag was not set in right way in the Database to activate SSL for the Page.