Hey Younes,

The space between the lines you are referring to is because you are starting a new paragraph. This is coming from the CSS (when editing it’s coming from the tinyMCE CSS, when viewing a post it’s coming from the theme CSS)

You can make style changes to these, also – you can press shift + enter for a soft return.

If you do make style changes, be sure to save them to a custom or child theme so you don’t loose the change upon updating..

Shout if you need any further help!