1 Push the statue forward
Push the statue forward through the open door. The main point here is preventing the walls from crushing you. The statue will be enough to stop them.
2 The walls will stop because of the statue
The walls will keep closing on until they stop because of the statue. Note that you need to push the statue as far as you can.
3 Go around the right wall
Run around the right wall into the area that opened up after the wall has moved. Go to the end of that corridor.
4 Press the switch you will find
You will find a switch at the end of that new corridor press it.
5 Run back fast
Run back fast to the place of the statue you pushed earlier. Note that timing is important here and that you must move as soon as you press the switch.
6 Push the statue to the left
Push the statue to the left until it stands on the grey square on the floor. If done right you will hear a sound and the statue will move to the back on its own.
7 A door will open in the wall
A door will open in the wall. Get through it and you will find a ladder leading downstairs.