If those flex cables are damaged or broken, your only option is replacing the screen. If you wanted to try it yourself, you need to move the OEM front sensor assembly to the new screen so you will still have Face ID. [link|https://www.mobiledefenders.com/apple-repair-parts/iphone/iphone-12-pro.html|Here] is a link to MobileDefenders, where you can choose which screen you want to get. They have three different options for the 12 Pro. Also, you will need an iCopy device if you want to have True Tone on the new screen.