If you want to buy a futures, you must have someone in the market to sell it at the same price as you, and then you can make a deal. If you sell and close your position, you can only close your position if someone in the market buys at the same price as you. Assuming that no one in the market buys it in extreme cases, you can't even it out. Generally, this will not happen because there are many participants and the transaction is active. As long as your price is right, business can be concluded.

Short positions are equal to long positions!

Buy a futures contract and sell a futures contract with a turnover of 2. You can see that the futures trading volume and positions announced by China are even, not odd.