http://track-chinapost.com/result_eub.php?code=LM334433644CN shows the parcel was shipped From China Post Guangzhou office to Greece on Dec 8.

It is now some middle location between China Post system and ELTA system(possibly airline warehouse in Guangzhou,China or customs warehouse in Greece ). You can not know exact situation when parcel is in such middle locations.

Such no-information stage might last 7 to 20 days(rush season can take 30 to 40 days) until ELTA gets the parcel from customs. Then ELTA website will show its new status with Greece location.

Everything looks normal. Please wait some more days.

http://track-chinapost.com/result_china.php?order_no=RN685448080CN 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, Bulgaria Post 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.