Never been good with gears... Any help..

So just picked this up cheap for a mate and the gears didn't work great so thought would give it a go.
Could get them working on the middle and biggest cog but not the smallest.
Even without the wire in the... Holder? Sorry I don't know the correct name, the chain won't pop down to the bottom ring. Ivw lossened the low end screw as much as I can but it still doesnt seem to move the chain down.
I'm sure I've done something very simply for someone that has a clue... Can you help give me a clue?
Little video to show where I am. https://photos.app.goo.gl/hH31ex7BPVMsYAMy8
Could get them working on the middle and biggest cog but not the smallest.
Even without the wire in the... Holder? Sorry I don't know the correct name, the chain won't pop down to the bottom ring. Ivw lossened the low end screw as much as I can but it still doesnt seem to move the chain down.
I'm sure I've done something very simply for someone that has a clue... Can you help give me a clue?
Little video to show where I am. https://photos.app.goo.gl/hH31ex7BPVMsYAMy8
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Bearing that in mind, I would say its your lower limit screw that needs a fiddle. Looking at the video, it looks loke both limit screws are unwound about as far as they can go and that doesn't look right to me.
You could start by disconnecting the cable from the mech and then:
1) Make sure that the cage is parallel to the chain (it looks like the font of the cage is pointing inwards but difficult to tell from your video)
2) Make sure that there is about 3mm clearance between the top of the highest tooth of the big ring and the bottom of the outermost side of the cage.
Once you have those sorted out, push the mech by hand to see if it reaches across far enough over the small ring that it would move the chain. If it doesn't you need to adjust the low limit. Holding your finger on it should let you feel whether you're going the right way as it will move slightly. If it doesn't move, you're turning the wrong screw, if it moves the wrong way, turn it the other way.
Once you've done that reconnect the cable and repeat for the high limit going outwards.
You may need to fiddle with it a bit more to get it tuned in perfectly on the barrel adjusters.
Thankyou for your replies. Sorry I didn't get a notification that I had responses.