Switching
The language switch in the header swaps the page you're on — it doesn't take you anywhere else, and it doesn't touch your data.
What translates
The interface and every help page exist fully in both Arabic and English. Your business data — customer names, notes, documents — stays exactly as you entered it.
Remembered
Your choice is remembered for next time, and every page keeps its own address in both languages, so you can share a link in either one.