Like others have said. Silicone spray is magic. Put a paper towel on the ground underneath it, spray the gaps a little, nove the door back and forth. Repeat a few times. Clean the outside afterward by wiping the excess.

Squirt/apply lubircant, open and close the hinge to work the lube in.

WD40 works as a lazyman's option, for a short time. However really WD40 is more of a solvent and not a lubricant - it will dissolve out any real lubricant, then dry out much more quickly than a proper grease and also possibly attract more dirt.

You can get plenty of other lubricant sprays. A quick search suggests things with PTFE (teflon) in them can be good. WD40 do a teflon spray can, that was the recommended lube for my crosstrainer.

Other, possibly better lubricants are silicone or lithium based.

Petroleum jelly can work also. Any lube is better than none, but this website suggests petroleum jelly < PTFE < silicone or lithium. However I'd defer to some proper science to decide which is really best.

That's a spring hinge - I would not attempt to disassemble it. For this one, I'd use a light oil, like 3 in one oil or sewing machine oil and just do my best to get it into the hinge, either through the upper hole with the bar coming out of it, or allowing it to penetrate down the seam in the center of the top. You'll probably need to work the door back and forth a bunch to get the oil where it needs to go.

I would use a spray lubricant with silicone in it. A Teflon one will work too but Teflon is horrible for the environment so I avoid them. Something like this

https://www.homedepot.com/p/Blaster-11-oz-Industrial-Strength-Silicone-Lubricant-Spray-16-SL/202529794

Or you could use a gun oil and squirter a couple drops on it.

I use white lithium grease (spray bottle with thin straw) in the hinges. Maybe you can find a way into the inside with the straw. WD-40 and similar oils are too thin for a hinge long-term.