Well what I feared at last happened.
This thread has already been translated:
I have no problem adding your translation to the OP but please next time try to coordinate, posting an "announcement" thread about which post are you going to translate, in order to avoid duplicated work.
From next time I will carefully evaluate the situation and only translation per language will be allowed.
The same translated article was just one post above and he should have taken a look on the same page but as he said he might have overlooked it and posted his work and now have made announcement here about his translation.
So make a rule that every member who is going to translate any of your topic should make an announcement on this thread beforehand to avoid any confusions and they should be looking at the @OP to check in how many languages the article have been already translated as it's lot of work and double work should be avoided.