how to create a picture and video page

Yes. You can install a plugin that changes WordPress in a picture gallery. Check out the WordPRess Plugin directory and search for such plugins.

can you just do it for a page and not the whole site

is there any plugins for videos to make a page for videos and folders

YEs typically such plugins are used to configure a section of WordPress to be a photo gallery, not the whole WordPress. So you will have a sort of website and a image gallery integrated with it.

thanks