http://track-chinapost.com/result_china.php?order_no=RP121693733CN shows the number was sent to airline on Dec 10.

China Post will lost control of the parcel after sent to airline. so there will be no update anymore after sent to airline date.

Sent to airline does not mean you will get the parcel very soon. It will keep waiting 5 to 10 days in airline warehouse waiting flight space and another 1 to 4 weeks import customs processing in destination country(speed depending on country). The status will stuck at "sent to airline" during this 2 to 8 weeks period.

Once it passes import customs clearance, Spain Post (correos Spain) will scan and update its new location for China Post database and you will see new status.

So you no need do anything, just wait some more time.