In the box there are just 5 dice. But in youtube, i saw that people are playing with 10 dice. Should i need 5 more or why dont they play it with only 5 dice? What is the difference?

Can you please inform me about it? Thnx in advance.

Five dice come with the box, but there are cases where you have to roll more than 5 dice (it could happen you roll even more than 10 dice). You have clearly two options: rolling five, remembering the results and rolling again, or getting some more dice. There are a bunch of great dice produced via Chessex ( here the link to the thread on BGG), or you can get the official Arkham dice licensed by FFG or you can use any D6 you'd like to use

Thank you so much for your kindness. I'll consider those opportunities.

Glad I helped And most important: enjoy the game

Another keep-in-minder: I've been playing since 2006, and rarely have I ever needed more than 12 dice on any single roll. Conveniently, most gaming stores/sites sell small blocks of 12 Chessex dice for cheap. I've put six of these 12-setters in my boxes so all my Cult members get a choice of their own dice...but I'm a dice enthusiast.

I've had a few occasions when I have needed to roll more than 15 dice. I keep 20 of each kind of dice: normal, cursed and blessed.

Really, if you do a lot of gaming, you are going to need a barrel of d6's. The official ones are nice, but any should work.