In the beginning, walk the way the game shows you. Mummies will attack you but they shouldn't be much of a problem because there will be traps on their way - you can use them to your advantage.
After a fight continue forward until you reach the first puzzle in this chapter. You'll just have to press three buttons that look like skulls. All of them are on walls nearby. First the one with a snake, then the blank one and in the and the one with a head.
After completing the puzzle continue forward, killing some mummies. At one point the floor will collapse under you and you'll be forced to slide down through the compound. Watch out for all kinds of obstacles, avoid them using the movement keys.
After you go all the way down, a lot of zombies will show up. The best way to defeat them is throwing grenades and letting the light inside by opening the windows. To do it you have to find a golden plate on the wall and shoot it. Then you can stand in the light and kill the mummies as soon as they reach it.
When it's over, the door on the other side of the room will open. Keep going and avoid the trap that may crush you if you step on it (watch your step).
Enter the next chamber, another puzzle awaits. Two skulls with symbols. Change the right one to an elephant and the left one to the thing below the hawk (whatever it is).
Part of the passage will unlock. Get on the first platform, shoot the golden plate on the other side and move along the new path.
Come closer so you can see the inside of another platform and shoot another golden plate there. Move along the new path.
You'll reach the exit. Go forward, there will be a place to distribute your skill points on your way.
Go forward and you'll reach a chamber with a mirror that reflects light. A horde of mummies will appear again. Using the mirror is the easiest way to get rid of them.
Enter another room, there's yet another puzzle. Walk up to the wall on the right side of the door and shoot the ring on the wall. Then come back to the lever in the middle of the room and take the skull. Put it on the right scale. You need to put three coins on the other one. One of them is in one of the tombs near the legs, the other one on the table on the right and the last one is near the lever.
After placing three coins and the skull on the scales, pull the lever. A way forward will open.
After a moment you'll reach another chamber that will test your reflexes. There will be some swinging blades on your way. Of course you have to walk between them. It should not be a problem because they're not very fast.
There will be a place to distribute your skill points on the other side.
Afterwards, turn right and go upstairs. You'll see a door with blue gems. You need to take the flashlight and focus the light on the correct ones to open it. The easiest way is to light up first circle at the very bottom and the rectangle that's not on the same ring as the lit up ones. Then the lock will open.
Go forward and you'll reach a chamber with another puzzle. Check the paintings on the walls and a page in your notebook. You have to walk according to the tiles' numbers. If you step on a wrong tile, you'll have to start over.
After reaching the stone tile check your notebook again because the symbols you have to step on have changed. Remember the order and move along the correct path.
After reaching the other side, another door will open.
Jump down and walk along the corridor while killing mummies in armors. You can also destroy parts of the ceiling above them to make it easier for you.
You'll finally go outside, distribute the skill points in a place nearby. Keep going and enter another place inside the building. Another puzzle is waiting for you.
Again, you have to activate switches the way your notebook shows you. In the middle of the room there's a mechanism that will lead you to the right ones. You can rotate the platform with a horizontal wheel and move it up and down with the vertical ones. The door will open after you press the right switches.
The Nazis will show up again, better kill them before you take care of the remaining switches. Be careful not to press the wrong ones or you'll get burned. Press only the one with a dragon on both sides.
Then go up and use the lever to finish the chapter.