Took me a little over 5 hours on my first playthrough (including all cutscenes)Not much replayability. You can't level up any skills or anything and there is no New Game+. And you cannot skip cutscenes either, so it would be the exact same experience I'm afraid. Pretty much the only side thing you can do is looking for collectibles, but that's it. No challenges or whatever.
Well maybe it's 2 hours or 2,5. I didn't measure the time, but the majority of it is cutscenes. So 1,5 hours or 2,5 hours doesn't seem like a big difference either way. Obviously depends on the player.
If you really get into finding collectibles I'm sure you can spend much more time with it. Or if you play on hard difficulty (which I wasn't). But my best guess, based on what I have captured it's around 1,5h-2h gameplay and rest was cutscenes. Take the first 4 chapters for example, maybe 35% of that was gameplay. Some chapters consist only of cutscenes. And often times there are these "interactive" cutscenes with QTEs where you need to press some buttons, but I wouldn't count that as gameplay.

Alter, da ist ja 50% cutscenes. Der Rest ist boring gun fighting. Das storniere ich lieber und hole es für 30€ in zwei Monaten.