Hello,
You don’t need to add any custom links. You need to use Language switcher widget and if page/product/post have translation user will be redirected to that language once click on the switcher button.
How to translate every post/page/product you can find in WPML documentation. It has detailed explanation with images.
If you want to remove any language go to WPML > Languages http://prntscr.com/jbvq6d . Where do you see DE? I see only 3 languages on your site – EN, ES, FR.
Regards