how many time it takes to beat the game?

I'm guessing an hour, maybe two?

I have just restarted the game several times to try to unlock it but I cannot find the solution I thought it was related to the bad guy armed on the roof or a fall to be achieved (all falls realised in one session, maybe ?) or some hidden place but I couldn't find anything. If someone could give me a clue to get it without giving me the solution, that would help me. I just don't know what I'm looking for because I couldn't find a painting or a lion figure on the map...

Judging by watching the gameplay trailer on Steam I think the character's moviment is too slow sometimes, jumping, falling, climbing and interact seems too slow. Also, I saw those 2 humans vanishing from nothing instead of being splashed by the car =) About the mechanics of the character's movement, it seems natural see the character running and walking in the horizontal way smoothly, but it's strange to see the character being heavy to do actions and move vetically. About the gore, will you implement a ...

Give me a hint on how to get one: Mufaso and F***ing Survivor.