The usual process is: write the English, get it approved, then hand it to a translator. By the time the Arabic exists, every decision, the rhythm, the wordplay, the length of the sentence, has already been made for a different language. The translator is not writing. They are salvaging.
Write the idea, not the sentence, first
The fix is to separate the idea from its first-language phrasing before either version is finished. Settle what the line has to do: reassure, provoke, simplify. Then let a native writer build the Arabic version toward that same job, in Arabic’s own rhythm, not English’s. The two versions will not be literal matches. They should not be. They should do the same work.
A tagline that only works in one language was never really a brand line. It was an English line the brand happened to also have.