Language switcher using Wordpress network

Hello, I would like to add a flag based language switcher to my website. I've found some plugins, but they only support page by page translation. I want to be able to select a language and all the pages I select then will be displayed in that language. It's possible to do so using a multisite ([login to view URL]). This creates a 'website in each language. I need Dutch (default), English and French for now. The subfolders for the domains need be like this: /be/postname, /en/postname, /fr/postname I still need to receive feedback on the position of the flags. The flags also needs to adjust according to the screensize. Website: [login to view URL] Also, if you have any suggestions to optimize the Google search results on certain keywords, that's a plus too! Kind regards, TOM