I think it's safe to assume that the inscriptions in the two languages contain the same message.
The reason that the translation from Arabic is complete and utter nonsense is because the language written here in Arabic script isn't Arabic. Looking at how Mao Zedong's name is written here and comparing it to the titles of Wikipedia articles on Mao in various languages using Arabic script, I'm going to guess that the language is Uyghur. This would make sense, because 12.8 million Uyghurs live in the People's Republic of China, primarily in the Xinjiang Uyghur Autonomous Region.
My opinion is that this is a postcard produced in Xinjiang, featuring an inspirational quote from Chairman Mao in Chinese and Uyghur.
https://en.wikipedia.org/wiki/Uyghur_language