No Text Weight on Elementor Mobile Website

I'm using the Elementor Page Builder for my website. On Desktop View, i made a big title with Arial and a Font Weight of 900. So its really fat. The same i did on Mobile and in the editor, the title is really fat. Now, when i go to my website on mobile, the title, which should be fat, isnt fat. It is still bold, but the weight isn't 900, event tough i selected 900 on mobile and desktop. I already tried to do something with CSS, but i'm not that good so...

Does anyone know how to solve this problem.

Thanks a lot guys!!