Hi! Glad to hear you liked the game despite some frustrations. At a basic level, the game is about collecting all three stars that unlock the door. Hence the game is also divided into three separate paths leading to them, making it a non-linear game. So the order of solving them would vary by players.
SPOILER BELOW
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You said you solved the fish puzzle, so I'm assuming you haven't got the other two items? You can get the plane by pressing the plane poster, which will make the plane appear through the window. The other one can be unlocked byfinding all the boat pieces.
Hope these are helpful!