The keyboard disappeared nad there is no keaboard on the keyboard list, I can’t do anything to add a new keyboard, since I can’t search or write… what should I do?
I would look in Apps and notifications (showing all apps) as find GBoard to see if it is enabled and enable it if not. It should be there if you are using the stock Android ROM.
If not, you could log into the play store from another device and load a keyboard onto your FP3.
Should you need to, you can also plug a physical keyboard into the FP3 USB C charger port but you’d need an adapter (USB C male to USB A female).
If, and hopefully you will find it, clear the cache and the storage associated with it.
Failing that start the phone in safe mode which will temporarily disable any custom apps you have that may be interfering.
If you, have a backup of your personal data and files, or you can make a backup you could try a factory reset.