You want to sell ads on your movies or you want to sell movies directly by promoting it?
I think you want to sell movies by promoting it.
I suggest to go for Google cloud as hosting because they have media service, which allowed to play your movies with different resolution and encoding formats.
To implement payment API, I suggest Instamojo but it support only Indian currency. Almost all payment service have call back API which can help you create your own sell reports, you just have to read their docs or contact the team.
You required experience developers for that or may be team as well but if you have no tight budget then I suggest to make a subscription page on your site like lynda.com, so if user buy any monthly package then they can view your private website after login.
On your private website, you add videos easily with HTML5 tag, but based on user subscription, you have to embed multiple files with different resolution and encoding formats, because many mobile device does not support H265 coding, and may be many people want to see your videos in 1440p or 2160p. so based on user you might need different formats for same movie.
I have no idea about price so please refer upwork.com, and I also suggest you do simple search on Google about “Sell your film”, you might find many good service with good rev share program, because building own platform from scratch require tight budget.