Hi, I found the solution without changing the ASTRA theme thanks to this:
“…The navigation buttons…”
I didn’t know what they are called in English and you were right it was a theme issue, I changed a line of code in the “theme editor” (Appearance/ theme editor/ functions.php) and copy-paste this line of code at the end of the file
add_filter( ‘astra_single_post_navigation_enabled’, ‘__return_false’ );
This was the result
Before the code
After the code
This is not permanent, whenever the Astra theme launch a new update it will removes the custom code and it will be necessary to install the code manually again.
PS: I tried to change the theme but I got a warning that I may lose data or even break my website.
PS 2: the code can stay pemanently if I create a child theme for the Astra theme.
thanks @dericleeyy for your advices. ??