5.Gang won’t go in

Hello, I have the following problem with our Audi A1, 1.6 TDI, 77KW, year 2013, manual gearbox key letter MZM with 210TKm mileage: After initially an increasingly difficult to remove reverse gear was noticed, it happened once in a while during the ride and then increasingly often that the 5th gear could not be inserted. There were no gearbox noises or gear lever movements during load changes. I cleaned the switching scenery and gear cable hoists, checked, greased, slip shoe changed and new basic adjustment of the rope hoists made. No change. I then checked/changed gear oil and found crystal clear oil without any turbidity or even metallic abrasion … I then have been told independently by 2 experts (KFZ mechanic) that “return gear goes very hard out and 5th gear is not pure” a well-known, frequently occurring problem with this type is still very happy and the simple solution is the change of the clutch set together. Although performance, despite the first clutch, until there is no problem with the clutch, now I did not have to look at least at the Resounding.