A friendly jigsaw

This puzzle belongs to the puzzle series: hyper-modern art

The two friends in the gallery of hyper-modern art move into a room which is painted completely in black and white. Strange, wavy lines cover the floor and seem to 'flow' together in the central painting, the only one in the room.

"Quite dull, I dare say. If you don't mind, I'll just move on to the next room."

"Wait a bit. I think you would be well advised to take a closer look at the painting. It is called friendly advice after all."

"Bah! I've lost my HUD and looking at all these lines makes me dizzy. I move on!"

The man turns around and towards the only other door leading out of this room. A security camera is observing it, but he ignores. The moment he touches the handle, he gets a mild, but still hurting electric shock and some alarm bell tweezes.

"Jesus! What's that supposed to mean?!"

"I told you," the other friend says with a broad grin, "One always has to look for hidden meanings in the gallery of hyper-modern art."

With that, he passes his confused friend, ignores his attempt to warn him, and grabs the door handle, opens the door, and walks on to the next room.

"Are you coming, or what?" he beams back at his friend.

"Sure."

But the moment he touches the handle, he is shocked again.

"WTF!" he shouts out, holding his aching hand.

"I guess you need to find your passcode first, my friend. Have fun, I'll wait next door".

The goal of this puzzle is to derive the one thing the one man knew and his friend didn't. The one thing which let him pass the door unharmed.

• A person can only pass the door at second try. Not serious. Jun 11, 2016 at 19:44

He has to

Smile

1st level

2nd level

3rd level

• Sell done. Btw: the other friend says with a broad grin and he beams back were two hints, too. Jun 12, 2016 at 5:55

Aww, looks like I'm late

Nevertheless, here's what I've done

Step 1