Hi there,
Though mobile was slightly slower, loading your site on both desktop and mobile was relatively slow.
I put the site through GTMetrix and it did score poorly:
https://gtmetrix.com/reports/www.schnellerabnehmen24.de/sIavy1sF
It is actually saying that many images on the site are not optimized. They give a link to the images in question, so I would take a look and see if you can further optimize the images.
Thanks,