How do I build a properly bilingual website? — answered by Engineer Saeed Baatiah
Four conditions: a separate URL per language such as /ar and /en rather than a JavaScript toggle on one URL, hreflang tags linking the two versions, correct page direction with a design that genuinely works right-to-left rather than merely mirrored text, and human translation for marketing content at minimum. The most expensive mistake is switching language on the same URL: you lose half your pages from indexing, because the search engine only ever sees one version.