Futures Contracts: Between Halal and Haram

I went to a car market and met a man selling a car for 50 cash units. We agreed on the purchase and sale, and I gave him 5% of the agreed price (I think it’s leverage) on the condition that I would complete the rest for him in the evening (if we applied this to blockchain, we wouldn't need the traditional principle of trust, but rather mutuality) (#P2P ) Back to the story, I do not intend to leave the market until I sell the car. If I sold it for more than 50 units, I would be in a state of profit, and if less, I would incur a loss.

Is there something wrong with the transaction that necessitates prohibition?

Does the prohibition of futures contracts necessitate the prohibition of dealing in dollars (the paper) instead of gold (the value)?

The important thing is to make money, even for the sake of charity, for only the poor man does not ask you where you got this from; he is simply overwhelmed with joy.

And Allah knows best

#MuslimCrypto