My screen is completely unstable, screws fell off.

I think you’ll need a bit more than the screws here. Looking at the vid it’s clear the hinge clutch is gone which is why the lid is not staying up. I’m on the road right now when I get back home in six hours I’ll post the needed parts as I don’t have my notes with me.

In the meantime stop using your system & power it down as you don’t want to damage the cables! That would make this a more expensive repair.

One last question looking at your picture it appears the shank of the screw is still present in the lid is that the he case?

IFIXIT offers the hinge/cable assembly but is currently out of stock on the screw set.

• MacBook Pro Retina (2012-2015) Display LVDS Cable
• MacBook Pro 15" Screw Set

TheBookYard in the UK also has the hinge/cable assembly

• Retina MacBook Pro 13"/15" Hinge, Left - LVDS cable (12-15)
• Retina MacBook Pro 15" Hinge/Clutch Cover (15)

When you talk with them ask them for a set off screws TheBookYard Ask for Jon or Nick, Tell them you posted a Q here ;-}

If the right also needs replacing (a strong possibility) you’ll need to go here as TheBookYard is currently out of stock: Aliexpress - iSight Camera Cable WIFI Antenna

OK, that takes care of the needed parts. The next issue is how to pull this off! Follow this IFIXIT guide: MacBook Pro 15インチ Retina Display Mid 2015のディスプレイアセンブリの交換. Once the display is free you can slide off the plastic clutch cover to replace the hinge/cable assembly and its screws. Double check the other hinge to make sure its in good shape before finishing things. Slide the clutch cover back on and follow the procedure pin reverse.