For a number of reasons, Mal. First of all, the translation itself has been described as nothing more than "blatant plagiarism" of a previous Qadiani translator, and there are doubts as to who "M. H. Shakir" is. Secondly, there are the obvious mistakes and inaccuracies in the translation as well. For example, in the verse you quoted, it seems as though Shakir is ignorant of the tafseer of this verse and the basic story of Prophet Ayub, because he translated "bundle of thin grass" as "green branch" - obviously the two are not the same. Beating someone with a green branch conveys a completely different meaning from striking someone with a bundle of thin grass to fullfil one's oath but not cause harm.
As I said before, the best thing for you to do is simply to look at multiple translations of a verse - some are more reliable than others.
Regards