Create a simple quiz I have a videos content type and I want users, who have watched this video, to answer some questions related to each single video.

How can I create a quiz for each single video node?
I tried the webform module and create a video block but there is a problem.
The  video will be shown in all forms and I can't insert video for next question.
Please help me.
You can always try the Quiz module. I have some experience with it and it mighty suffice for your needs.

Or you can always create your own form with the well-documented FormAPI. You can define your own validation- and submithandlers. Very, véry cool features.
What you can do is create a custom block, and fill it up with your own form. 

Depending on your experience level (and time), you can one of above options...
Good luck!