Guys was there any universal sign for help during ww2 if you were hopelessly lost,in danger or hurt.

I'm not exactly sure what you mean? Is it a sign to be seen by air? Seen by another GI or soldier? A hand signal, or a gesture? Whats the storyline?

I dont know if this is what you intend - but I think flying your flag upside down is universally accepted as a distress signal...

Story line:
German patrol lost in the desert and dieing of thirst, and need help fast from anybody.

Well... I think that by the time all their water was gone, they would have gotten rid of all their other stuff too...that is if they where on foot....

FWIW -
I agree with Eagle.
You might go heavy on the weathering, of the face and especially the lips.
Show some opened canteens laying by a jeep theyre trying to drain the radiator from or something???
BUT
I still cant think of one symbolic way for you to get that message across, but I wish you creative success
Maybe if you could find some figures where normally one Afrika corp is supposed to be helping another who has been shot, you can make them appear instead to be dehydration/sunburn victims also

Only guessing, dont know how this would go for other countries, but you could write a big "S O S" in the sand?????
I guess a white flag is surrender in every country as well!

Hmmm... if it were me, I would use the boot heel and scribe "H-E-L-P" in the sand! Then to make sure it was seen, I would line it with neon lights, a 5000KW searchlight, and then set up a global broadcast device to tell people I was really getting desperate. The only problem would be finding an electrical cord that was 300 miles long.

Either that, or I would get our my notebook pc, logon to Armorama, and tell PlasticBattle to come find me!

Hmm...Uh..You could try getting the word "HELP" in German....Or..since the German language is close to the English Language, you could try going to your local library to do a research on German words that spell and mean the same in English - that way, I think, will give an impression that these desperate soldiers hope they can be found - by friend or foe...

Good Luck on your work!

Try HILFE