How to offer my YT skills to companies?

Hello guys, sorry for my English. I am Greek and i learn some English be myself, reading forums and watching videos.

I made a YT channel 13 months ago and now i get 1-3 millions views per month. With adsense i make 2-3k $ and its keep growing very very VERY aggressively. I dodnt do vlogs etc, so it doesn't matter that my english sucks (thank you God). I live in Greece, i can keep make 1 video per day (3-4 hours work) and grow, OR i can invest more time and make more things.

I know YT very good, and i was thinking about this idea:

I go to a Greek eshop and tell them, that i can make a YT channel and unboxing their products and grow a channel with the name of thier company, build relashionship with consumers etc and sent traffic to eshop. I think i can do that very well, and i see many big companies dont use YT witch is insane. My question is this, how the hell i will protect myself to not grow a channel and get "fired"? If i will have the channel, they will never agree (i guess) but i cant let them have it etc.

I dont know if you guys get my problem, and i really cant ask for advice in Greeks forums.
Thank you!