They say that the observable universe is only 5% of the entire
The observable universe and regular matter are different things.
Regular matter is the stuff that you and I are made of. Besides regular matter, the Universe is made of dark matter and dark energy. According to some estimates, regular matter is indeed only a few percentage points of the "stuff" in the observable universe.
Dark matter - it's not clear what it is, but it appears to be matter-like and it interacts gravitationally. It does not seem to interact in any other way; it could be shooting right now through your head and you wouldn't know it. It does not make clumps like regular matter, so it tends to stay in a diffuse state. That's all we know about it, everything else is speculation.
Dark energy is something that drives and accelerates the expansion of the universe but doesn't seem to do anything else. It is not related to dark matter despite both being called "dark". That's all we know about it.
The observable universe is the chunk of the Universe that we can see: regular matter, dark matter, dark energy, and the space in between. By definition, the observable universe is everything that we could (theoretically) observe or detect. It's basically everything within a radius of a few dozen billion light years measured from the chair you're sitting on.
Anything placed further than that is outside the observable universe and by definition cannot be observed. Not only that, but it cannot influence us in any way whatsoever - if it could, it would be observable.
sort of like how galaxies redshift and slowly face away of out
That's a tricky statement.
The universe expands. Things close to us (on a cosmic scale) are drifting away from us slowly. Things far away from us are drifting apart quickly. Things very far are drifting away very quickly.
Keep going like this and there comes a place where things are drifting away from us at light speed. Beyond this threshold there's nothing for us to see anymore. That's the theoretical outer limit of the observable universe. Anything beyond it is outside the observable universe. In practice you can't quite see that far anyway, to be honest, because at those huge distances it's hard to detect anything, and because at those huge distances you only see very old objects which may not be bright enough yet to be seen (before stars are formed).
It is true that once something is out of the observable universe, it's basically as if it doesn't exist anymore. But that's only true from your frame of reference. From their frame of reference they continue to exist just fine. Both frames are correct, BTW. Disagreements like this one are common in relativity.
So don't say they're fading out of existence, because they may get angry at you. :) Simply say they exit the observable universe.
does dark matter/energy increase every year?
Please be aware that anything that gets out of our observable universe, be it regular matter, dark matter, or dark energy, is lost to us forever. The event horizon (outer limit) of the observable universe does not apply only to regular matter, it applies to everything.
That being said, within the observable universe, we don't really know if the relative percentages of regular matter, dark matter, and dark energy are changing a whole lot.
What comes after red shift? Black?
Red shift does not have a limit. The name seems to suggest it stops at red - but really it doesn't. It's just not a perfect name, that's all.
As things move away from you faster and faster and faster, light coming in from there gets "red shifted" - it simply means the wavelength becomes bigger and bigger and bigger. If light starts out in the color blue, "red shift" just means it becomes green, then yellow, orange, red, infrared, microwave, radio waves... just getting stretched out more and more.
At some point the wavelength gets so big it becomes very hard to detect anything.
How do you measure something that has already left the observable
You don't. It's out of OU, it's gone. Completely and forever. Just let it go cause it ain't coming back.
does that mean the universe is mostly black because 95% of matter has
The universe is mostly black because there's not enough regular matter (stars, more specifically) in the observable universe to light it up fully. It's just a whole lot of empty space - hence dark.
It is true that in the outer parts of the observable universe objects are so red shifted that it's hard to see them anymore. That's one thing.
The other thing is - once objects are so far that they are moving away from us faster than light speed, it is 100% impossible for us to see them, forever. They are completely outside the observable universe.
So, the night sky is dark because the observable universe is not infinite, and because it's mostly empty. This is the solution to Olbers' paradox.