How to flash firmware to your phone:
WARNING WARNING WARNING -> Before flashing, ACTIVATE PIN in "Secure startup" (You'll be asked for it AFTER flashing!)
2. Download Odin v3.12.7
3. Extract Odin ZIP file (i.e. to folder c:\Odin)
4. Open Odin v3.12.7
5. Reboot Phone in Download Mode (press and hold Bixby + Power + Volume Down buttons)
6. Connect phone and wait until you get a blue sign in Odin
7. Add the firmware files to their designated slots
8. Make sure re-partition is NOT ticked
9. Click the start button, sit back and wait few minutes
Below a video with the "How to flash"; thanks @ISF for making this tutorial:
*** You can always find the LATEST firmware in msg #2