[The question is more of which one he should be learning first, which he takes a few minutes to dwell on before sending another answer.]
Sign language first.
[He can communicate with his followers perfectly fine, at least, so he'll mainly need Arabic if he ever needs to do research or similar in Egypt. For now, that's not really a priority, so he'll go with the one that might be of immediate use.]
no subject
[The question is more of which one he should be learning first, which he takes a few minutes to dwell on before sending another answer.]
Sign language first.
[He can communicate with his followers perfectly fine, at least, so he'll mainly need Arabic if he ever needs to do research or similar in Egypt. For now, that's not really a priority, so he'll go with the one that might be of immediate use.]