By process of elimination, try your charger/cable combination on another device (compatible with super fast charging) to check if it's still super fast charging. If it works on the other device, then that would point to your phone being the problem. If it doesn't work, then that would indicate a fault with either your charger, the cable, or both. Source another known working charger and/or cable. You say you're also getting the moisture warning. Has the port come into contact with any liquid lately? Have a close look at the charging port. Look for any debris, fluff, etc. Blow it out, but don't go poking any metal objects in there!
You mention an update too, so can you try a cache partition wipe to rule out any corrupt files.
Plug into a working PC or laptop or other Samsung device
https://www.samsung.com/uk/support/mobile-devices/how-do-i-clear-the-cache-on-my-device/