@Rangod,

Please find the response to your queries below.

1/Could you please explain me how to remove some links or zooms on photographs on my front page (section Portfolio), from my WordPress Dashboard?

To remove link icon only

.hoverbutton i.fa.fa-link {
    display: none !important;
}

To remove zoom icon only

.hoverbutton i.fa.fa-search {
    display: none !important;
}

2/Is it possible to insert a movie in’Personnalisation’ ‘Section’ ‘About’?

Currently movie can be only inserted in ‘Testimonial’ section.

3/Still in my front page ‘Section’ ‘About’, is it possible to translate PURCHASE in an another langage from the WordPress Dashboard?

Since this theme is already translation ready, yes you can translate theme in any language.
There is .pot file available in /languages folder inside the theme. You can use Poedit software to translate theme as a whole.

For more detail refer : https://premium.wpmudev.org/blog/how-to-translate-a-wordpress-theme/