Change the language of my wordpress from the front page

I've been trying all day to change the language of my wordpress theme from an option on the front page nav, I've done the corresponding translation files and the language change works from the back-end. I have managed to get the list of available languages by the following function:

wp_dropdown_languages(array(
   'languages' => get_available_languages(),
   'show_available_translations' => false,
));

But I do not have a button to accept the selected language and change the content of the page. If anyone has any idea how to do this, I would appreciate it a lot.

I have also tried to change the variable $ GLOBALS ['WPLANG'] and send the language for another type of form but nothing worked for me