In order to get the key for the church in Chapter 4 of Resident Evil 4 Remake, you have to enter the correct combination of symbols on the desks with pressure surfaces in the small and large cave with shrine. You can find out what the solution to the puzzle looks like here.
Desk with printing surfaces in the large shrine cave
In the large cave with a shrine southwest of the lake, you first have to fight your way through a cave system until you get to a desk with pressure pads. Various symbols are shown on it. Your task is to hit the three correct symbols. If you answer correctly, the door will open in front of you. If the answer is wrong, the puzzle will be reset.
You can also watch the solution quickly and concisely in the following video:
You can get clues to the right solution if you look around carefully. Yellow symbols are shown at various points in the cave. One thing is only fully recognizable when you are in the right position and looking in the right direction.
Press the corresponding symbols on the console so that you can solve the puzzle. The order in which you press the symbols does not matter.
In the chamber behind the door you can Apostate’s Head take on you.
Desk with printing surfaces in the small shrine cave
In the small cave with a shrine northeast by the lake you will find a second puzzle with such symbols. Again, you need to look around the area to spot yellow icons from the right perspective. This gives you the clue to the solution.
Press the following symbols on the console with printing areas according to the instructions:
You can find him behind the door Head of the Blasphemer. You can also find one of the hexagonal pieces and a treasure here.