Answer is: pieces will be 5,7 yard long.
The length of all four pieces of a goal post laid end to end is 22,83 yards. That includes one 18-foot crossbar, one 10-foot base and two 20-foot arms for a total of 68 feet or 22,83 yards. If calculate that im meters, that will be 20,87/4 = 5,21 meter by piece.