Hints: the white dude always shows you the secret places. So always look at where he spawns.
There are three secret places you need to find:
-in the red area: left portal, then get to bottom left, to find a hidden portal, then interact with the first tree, but do it UNDER that tree.
-in the green area, after you give the rake, and the new portal opens, go to the bottom right portal and interact with the first top block (near which the white dude shows).
-after you beat the octopus, the pirate will open the portal to another place, there you should go bottom right to find the area with blue painting.
How to beat octopus: just go down under the octopus plate / painting / whatever and stay there. Try to be a little in the middle between the rocks, so you'll be untouchable.
At first I didn't like the game, but after a while, I started to dig it. Good work, albeit needs some polish.