I finally gave up on youtube's weird act. I uploaded the video several times, saved it even in different ways and it still looks tiny to me! I think that it is some kind of dysfunctional relationship with firefox, because it looks fine in explorer.
So, if you go to the channel and looks tiny to you, please try explorer. I think it looks fine in Chrome as well.
Here's the Part 2 of the video.
That's it for now, have an awesome day and keep your paintbrush wet!