Dear Pacifique,
1. To remove the testimonial background image, please follow this path:-
Apperance->Customize->Home Main Content Area->AT testimonials Section
Remove select Background Image
2. To make the menu unclickable and submenu clickable. Then go to:-
Apperance->Menu->Home -> URL-> #
Set URL to # for other menu also to deactivate it from being clickable.
Best Regards!