Your Gravity Forms version is out of date and should be updated.
Gravity Forms does not have a separate language setting. Gravity Forms will be output in the language that the site is set to. I’m not sure how they are changing the language, if it’s not actually Spanish language in the forms they created.
If you remove the plugin files only from the wp-content/plugins/gravityforms folder, and replace those files with a new copy, so forms or entries will be affected. That’s the same as updating the plugin with a new copy. If they previously modified any plugin files, updating the plugin would overwrite those changes (in your case, if they modified plugin files to output in Spanish, the update would reverse those changes.)