vimeo embedded in element grid - slow on mobile and scroll issue

[Nzagamba]

I embed quite a few videos in my Element Grids. I use the laytheme function to add the vimeo videos.
The vimeo videos are set to autoplay, muted, and loop.
Here is my page
There are a few issues I face:

Desktop:

• First video somehow loads very very slow, the videos further down work great, why is the first video not playing directly? It shows a black video for a long time, before playing.
• scroll issue: when scrolling down over a video, somehow scrolling blocks and slows down. Why? Can I turn this off?

Mobile:

• Videos on mobile don't load, or load very slowly, why is this?

Is there any way, I can improve these bugs?

[Nzagamba]

I just tried to play with the caching settings, and found out the following:

In Lay Options I ticked:

✅ Enable Layout Cache

-> makes first video loading very slowly, rest of the videos loads correctly.
-> my beautifully customized filter menu on desktop with js features breaks, when this is active.

✅ Disable Ajax / Compatibility Mode

-> makes first video not load at all, rest of the videos loads correctly
-> my beautifully customized filter menu works now.

I'm wondering now, If my site gets slower, if I don't activate caching? Should I then use a caching plugin like WP fastest cache? I can't tell if the site is faster using WP fastest cache...

and how do I get my first video to load?

PS:
scroll issue is solved after deactivating ❏ smooth scrolling