Hello :)

So, the diameter² would be: 2²+2²=8
radius²=4
area of the full circle = 4pi
area circle - area square = 4pi - 4 = 4(pi-1)
since it's only 2 parts, the pink area would be:
2(pi-1)

If I didn't miss something :3
Anyway, thanks for the opportunity :)