Google translated from Romanian:

Hello!
I have a problem at a 2005 unimog u300 with the gearbox, until the 4th goes and from the 5th speed only goes changed it remains stuck in the 4th !!!
What to do if you have an idea!
Thank you!

 

Does it have EAS automatic shifting? When was the clutch fluid last changed? Is there an error message under KS or GS?

C

 

Numi schimba de loc vitezele nici pe manual nici pe automat am luat o alta maneta dar nici cu aia nu vrea sa mearga delec de unde ar putea fi problema

 

Translated: "It doesn't change gears at all on manual or automatic, I got another lever but it doesn't want to go with that either, so I don't know where the problem could be."
So it is EAS. I would suspect an electronic shifter first. Does it go in "Neutral" at all? What are the error code readings?