The convertible sofa bed Multy by Ligne Roset supports 3 positions: sit, relax, and sleep. Usually, upon arrival it should be in "relax" (the back rest is less steep).
In order to switch from one to the other, you have to tilt it to the back, lift the sitting area while pulling it a little bit such that the backrest is in a horizontal position (see pictures). Starting from the "relax" position, lift the seating area until it "clicks" once, then it is in "sleep" position. When starting from the "sit" position it goes to "relax" after the first "click". Keep lifting until the second "click", then it is in sleeping position.
Starting from the "sleep" position, lift the seating area until it "clicks" once, then it is in "relax" position. Keep lifting until the second "click", then it is back in "sit" position. It is important that the part of the frame with the rear feet stays on the floor, don't lift this part (see pictures). Check out this video, it's really easy.