I used to have a language switch in my navigation menu, but it dissappeared and I don't know how to get it back. It used to appear on every page next to 'contact'.
To add and customize language switchers go to WPML → Languages in the WordPress dashboard.
From here, you can add new language switchers to the menu or a widget, in your case it is probably Main Menu, or you can edit the default language switcher in the footer.