Deadlift, upper back problem

[basalt]

Hi,

I somehow can't manage to get a straight upper back in the starting position of the deadlift... Is there any crucial step I am missing?
I've also tried to get into the starting position by performing a Romanian deadlift, my upper back is fine until the barbell is about to hit the ground.
It feels like the barbell is too low to reach it with a proper upper back. Does anyone have an idea why I can't do this properly? Is this a mobility issue?

Sidenote: I have some problems with ankle mobility during squats, I can't squat without any weight. If I try to do so I'll fall backward. I have no problems when squatting with weightlifting shoes and a heavy barbell on my back. Is there a chance that my ankle mobility also causes my upper back to round?

Thanks in advance!

[Pete Troupos]

A video would be helpful.

[basalt]

Apologies, I thought the video was included aready.
The insert video button does not work for me apparently, here's the link: dl on Vimeo

[Pete Troupos]

This doesn't look like the setup we teach. You're hips are way too low and the bar isn't on the shins.
Also, sets of 5 are requested when looking for a form check. Review the 5-step Setup™ for the deadlift on our YouTube channel. Get your shins on the bar and keep your hips higher.
Please use YouTube or something else for video. You can make the video unlisted and then just link it over here. That would be best. Thanks