Yes. Gravity Forms and Contact Form 7 can co-exist in the same website. They each have their own dashboard sections, and each have their own shortcodes and database tables, which should enable them to co-exist in the same site.
Gravity Forms and Contact Form 7 are WordPress plugins that offer contact form functionality. They each have a huge user base, totalling millions of WordPress sites. Mostly, website owners would choose one or the other to fulfil all of their contact form needs, but occasionally need to use both if their requirements cannot be totally met by one of the plugins.
Our preference is towards Gravity Forms, as it seems to offer the widest range of capabilities, and has a large number of addons that extend it’s use even more. However, Gravity Forms licences need to be purchased – at the time of writing a 1-site licence costs $59. Although Contact Form 7 is free, we’re happy to pay for premium WordPress plugins as this usually means better support, and plenty of updates to improve functionality and fix issues.