Hello Manuel,
If you want to remove menu from 404 Page, you have to edit some line of codes. If you are familiar with WordPress codes, you can edit it easily. Please find the code on 404.php and edit it. There is no any simple click and remove options available for it. If you are not familiar with WordPress codes, it would better you hire customizer to complete your task. Our dedicated customization team will add your requirements. http://www.acmethemes.com/customization-request/
Regards,
Thanks