My google pixel 3 has a black screen but is still responsive

Hi

Try shining a torch at an angle close to the screen when the phone is on to see if you can detect any images at all. They will be very faint if they are there so trying this in a darkened room may help to see them.

If there are images seen then there is a backlight problem with the screen. Not that this helps much knowing this at this stage but it might depending on what further testing shows.

If there are no images seen (or even if there are) then as a DIY repair all you can do is to open the phone and check that the display flex cable is still securely connected to the systemboard and if it is, is to then temporarily replace the screen and to check to see whether the problem is in the display or on the systemboard.

More likely it will be internal damage to the delicate connections in the original screen itself due to the fall.

If the replacement display is also black but there are images to be seen when using a torch then it might be a problem with the systemboard backlight power circuit to the display (fuse?)

Here’s the ifixit [無効なガイドリンク] guide which will help. Note the difficulty rating.

Replacement screens are available from ifixit ([リンクされた製品が存在しない、もしくは無効: IF356-050-2]) or elsewhere online. Just search for Google Pixel 3 OLED display to get results.

If doing all this seems too daunting, contact a reputable, professional mobile phone repair service and ask for a quote.