I am assuming here that there is no alternative to opening the Private Safe app, unlocking it and copying the files from it, because unless frankly if there is another way then that's a serious design fault (I don't have an Oppo so cannot test). So, assuming that is the case I have two questions:
1) Is it just the display that's gone, or is the touchscreen dead as well?
2) Does this device support any type of screen mirroring, specifically something that doesn't require you to do something in order to enable it?
The reason I ask is that you need to interact with it, and you need to be able to see what you are doing. If the touch layer is still working, even if the display is not, you can use that to interact. If not then you should be able to use a keyboard or mouse via a USB OTG adapter (cheap if you don't already have one), or a bluetooth keyboard or mouse if you already have one paired and it auto connects. Many phones support mirroring via HDMI if you have a suitable connector, but I don't know this model's specs. Wireless mirroring (e.g. via a Chromecast) is also possible, but you need to be able to start it (and set it up if you don't already have it) whereas wired mirroring, where the device supports it, should just start when you plug it in (at any rate it does with the older devices I've used it with).
So if you have a working touch layer and can mirror via a cable to a TV or monitor, you should be able to get into the private safe, remove the documents to somewhere less secure, then email them to yourself or copy via USB (or using the SD card if it has one). If don't have a working touch layer the challenge is to get mirroring and mouse/keyboard input working at the same time (wired screen mirroring plus a bluetooth input device, or wireless mirroring and a USB input device). This works great once you've done it, but getting it set up when you have to swap between interacting (wired keyboard/mouse) and seeing what you are doing (wired mirroring) is "fun". I have actually done this: unlocking a phone, getting to the bluetooth settings and pairing an input device to it by swapping between interacting and seeing (see where you are, plan your next move, swap to input device, attempt move, swap back to mirroring, see what happened, plan next move, repeat ad nauseam and beyond), but it takes patience. The good news is that at least the fingerprint scanner works, so you don't have to enter a PIN blind before you can do anything else!
