What are the perfect settings to take pictures of the moon with iphone 12 pro max ?

as you have discovered, the moon is very bright.  so bright that you should use the same exposure settings that you would use in normal daylight.  that can be a problem with a camera that does not allow you to set the exposure manually. 

slow shutter speed should do it . its called burning an image to let in more light so the background is clearer .fast speed only lets the moon not as clear and no background image .i have taken many night shots and find the slower speed is better for night time photographs .

You need to decrease the exposure.  Cameras will get fooled by the black area around the tiny Moon.  A camera's meter works by taking a reading of the light reflecting back from the subject.  It then comes up with an exposure to render that light level as a middle gray tone.  Since your phone is basically looking at a scene that is 95% pure black, the entire image is going to be way overexposed if you do not do anything.

Next to our Sun, the Moon is the brightest object in the night sky.  On the Moon it is daytime, so your exposure used for the Moon should be equivalent to what you'd use to photograph something here on Earth in daylight.

To solve this problem, you must be able to lower the exposure of the image.  You can do this by lowering the ISO, increasing the shutter speed, decreasing the aperture or some combination of all three.  Most phones don't have separate controls for the shutter, aperture and/or ISO. Most phones don't even have a variable aperture.  Therefore, you will likely need to use your phone's exposure compensation.  Set it to something like -3 or lower if needed.  If that still does not work, then placing a dark filter like a pair of sunglasses, an ND filter or polarizer over the lens will cut down the amount of light.

Does your camera have an exposure compensation control? If so, use it.

You'll need to set it to some negative number, perhaps -2 to -3. See if that helps. Be sure to set your exposure compensation back to zero when done shooting the moon as most cameras store this setting.

If you have manual exposure control, use it as it is a much better method for shooting the moon. The moon is a very bright object.

Perhaps this article will explain how to use your camera function:

https://ios.gadgethacks.com/how-to/control-focus-e...

The main thing you are doing wrong 

is using a phone camera to take pictures that call for a real camera.   

If it comes out bright, you'll need to make the shutter speed faster or lower ISO or both.