Q: My car has lost 5th gear

Unfortunately, your transmission probably has an internal mechanical failure. You should still attempt to rule out a problem, or maladjustment, in the shift linkage, of course, but if nothing is amiss with the linkage, the transmission has to be removed from the car and disassembled. Of course, due to the labor involved in removal, disassembly, cleaning, inspection, repair and re-installation, the entire transmission should be rebuilt, as needed, and that would start with inspection and measurement. Some certified Mechanics in the YourMechanic network are capable of performing these type of rebuilds, but you will simply have to check with YourMechanic to see if a Mechanic is available in your locale. If you have further questions or concerns on this or other vehicle issues, by all means please re-contact us and we will help you further.

The problem started with the synchronized gear worn and grinded the gears until the gears worn down and now you have no gears for fifth. You should have the transmission repaired or replaced.