The canonical tag mentioned first in your question should be the correct one.

However, you have an SSL certificate and your page appears correctly with the security icon after entering https://www.softedu.eu/ However, you have not entered the url with https in the 'URL of the website' field in WebsiteX5 in step 5 'Export', selection 'Export the website to the Internet'. You still have to adjust this and then click on the preview button while holding down the Ctrl key and wait until the progress bar has run through completely. Then upload the entire project, not just the changes.

In addition, you should ensure that your website is always redirected to the secure https site. If your web host does not have a way to force the redirect to the https page, you must create an .htaccess file yourself or add to an existing htaccess file. To do this, use the Windows Notepad to create a file with the following content:

RewriteEngine On

RewriteCond %{HTTPS} !=on

RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

Save this as htaccess.txt, for example. Then rename it to .htaccess (yes, the dot has to be in front) and load it into your server directory (where you upload your homepage). This means that every call to your site is automatically directed to the https site.