Technical Shifting to 3 and 4 gear

[jidebl]

Please my fiat ducato2.8idtd gear 3 and 4 is not engaged anymore, is gear 4 that had problem about 3 weeks ago but now gear 4 too did not engaged again. What do I do please the engine carry big gear, I have other that is only reverse gear that is not working, is of the same type I can I repair the gear with the damage gear from the one I removed initially

 

[bugsymike]

If it goes into 3 and 4 , tries to pull , but the revs go up but doesn't go faster and gradually gets worse in the lower gears along with a strong smell like hot brakes, it could be your clutch burnt out and not your gearbox.
However if makes noise from gearbox but no drive more likely the gearbox if only in certain gears.
Have a good mechanic test it.