I'm gonna share the solution to this quest created by one fo the players so you can find all of the pieces.
1. By the grave lake to the left.
2. In the forest between grave and hotel, closer to the grave but right at the "frontal edge" of the island.
3. in a tree trunk right from the hotel in the background.
4. By the lake close to that 3rd piece in the background.
5. At the harbor move your screen a bit right and down and find it on one of the stones, close to the left edge of the island

I have another problem - I cant find bottom piece, i clicked on everything I think.. upset that I can't solve that. Help me,please Q_Q

You can join our Discord server. One of the players posted a message with screenshots on where to find the shards :3 This is the exact message:
https://discord.com/channels/713012137538093067/1237738425961156698/1409844934797820056