1), it should be said that the net head is 5000, and the net long position is -5000!
2), see 1).
3), see 1).
4) liquidation: wheat and corn need to be sold; Soybeans 1, 2, 3 need to be bought. For example, stocks, most stocks can only be long. Then, opening a stock is to establish a long position, and closing a position is to sell this long position. It's just that futures can be long or short, so you can buy or sell positions from the beginning. In order not to be confused, you can use the starting and ending positions.
5), you are now a multi-position, that is, a long position, that is, a position of corn and wheat;
There are also short positions, that is, positions holding soybeans 1, 2, 3.
An empty warehouse has two meanings: the first meaning is 5); The second level means that there is no position in hand, neither long nor short.