You can say أنا آسف لخسارتك (ana aasif li khasaaratek) Also, this is a very common expression : رَحِمَهُ الله (rahimahu allah) if the person who died is a male رَحِمَها الله (rahimaha allah) id the person who died is a female This expression means : May God have mercy on him / her You can add أَسْكَنَهُ الله فَسيحَ جِنانِه (Askanahu allah faseeha jenaaneh) if the person who died is a male Or you change the 1st word to أَسْكَنَها (askanaha) if the person who died is a female. Maybe this 2nd expression is a bit hard, it means : May God makes him / her live in his wide heaven.

if he is muslim say ina lelah w ena elyh ragaaon انا لله وانا اليا راجعون

It's preferable to say رحمها الله as in, may God have mercy on her soul. As well as saying البقاء لله which more or less means only God survives death. My condolences: تعزياتي الحارة

أنا آسف لخسارتك

أنا آسفة لخسارتك