1999 Cabrio manual transmission not shifting properly
 

1999 Cabrio with 5 speed manual transmission will not go into first gear without pushing the shifter down like when putting the car into reverse. The car still runs and drives but could be a problem if first gear was missed and it went in to reverse instead. It's going to a new driver so I would like to get this fixed to avoid a potential accident.

Does anyone know what this might be or how to diagnose it? Also any tips on replacing the damaged or worn out parts.

Thanks in advance.