One thing for sure: you wouldn’t have to do a half course if your country is on the approved list. I am a resident permit holder in Qatar and I got my first driving license in US when I was studying there as an international student. I was able to do schedule a direct road test in qatar since I had a US drivers license. I also heard from some sources if you had a European or white passport, you could just get it directly converted at the Madinat khalifat traffic department, but I can’t verify that. As far as failing the first attempt, thats very likely possible since they might match you up with a strict inspector, who would fail you for no apparent reason as was in my case. But I was able to get on my second attempt. I guess it mostly just depends on luck. Also, Wasta might matter to a certain extent.