Hi Amy,
As best I can tell, it looks like the flex cable that's supposed to connect the LCD to the phone is broken; I'm guessing it tore off at the point where it goes through the opening in the frame (that square in the frame on the right). Here's a picture of what the flex cable should look like on a new screen.
Unfortunately it's not possible to repair that cable, so your only real choice here is to replace the screen. From your description, I'm reasonably confident that all it needs is a new screen, but it certainly wouldn't hurt to get a professional opinion, especially if you can get one cheap or for free.
All of the written, step by step guides I know of describe replacing the screen only when it comes already mounted on the frame, but in your case it would seem to make more sense to just replace the LCD without the frame since the two parts are already separated. Make sure your frame isn't damaged or bent though; if it is you'll want to do the whole frame+screen assembly rather than just the screen.
Here's a YouTube video that looks fairly reasonable in terms of showing you how to replace your screen by itself.
OPPO A5 2020 Display Replacement and Deassembly - YouTube
Should your frame be damaged, you'll want to use this guide instead.
Full screen (frame + screen) Oppo A5 (2020) repair - Free guide - SOSav
The screen itself seems to be readily available and pretty inexpensive; check sites like Amazon, eBay and AliExpress. Here's one that came up on a cursory search.
Black 6.5 Inch For Oppo A5 (2020) Cph1931 Cph1959 Cph1933 Cph1935 Full Lcd Display Touch Screen Digitizer Assembly Replacement - Mobile Phone Lcd Screens - AliExpress
Good luck, Amy; you can do this! Let us know how it goes, and feel free to ask for help if you need it.
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