After finishing all the levels with 3 stars and obtaining the hearts on all of them, I noticed that the counter for this achievement is stuck at 6 / 20. It's likely that only the first level with this quest (Level 5) correctly registers the count. I managed to get the achievement in the end by repeating level 5 until the counter reached 20....

Hello everybody! Could someone tell how to get this achievement? I never encountered any seagulls chasing. Thank you very much in advance!~