Hey sorry but without proof and without a chain of title proving where it came from you can't add "first bitcoin painting ever" to the price. Historical value comes from documentation.
How can I prove that I am really the first?
You probably can't unless you bought it around when bitcoin first came out and have documentation of that purchase. If you made it yourself and you made it recently it's not really that valuable. It's not a bad painting but just randomly doing something and claiming your the first one to do it isn't anything special.
The painting itself isn't that intricate either. It's a single color with the bitcoin symbol on it. It's cute but not really worth $100+.
