I want to learn more about OpenVINO but I don't know how I can.
Is there any tutorial step by step explaining how to make a simple program that can detect a vehicle for example ? (I have the samples but I didn't learn a lot from theses).
Perhaps if you read the samples/demo code along with the online docs for samples and demos things will become clearer. I understand your struggle - OpenVino has a steep learning curve.
You can also watch Youtube videos on the OpenVino Channel:
There's a bunch more videos done by this guy (who ironically is named "Guy"). Check him out on Youtube !