When I'm praying, how should I reciting Al-Fatiha should I start with the first Ayah which is "Bismillah Arrahman Arraheem" or should I immediately start with "Al-hamdu Lillahi Rabbil al-Alameen"?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

The verse (Bismillah ar-Rahmaan ar-Raheem) is to be recited before al-Faatihah during Prayers that are said aloud or quietly. The preponderant opinion is that both practices reciting Bismillah aloud or quiet are proved from the Prophet Muhammad . But the Prophet used to recite it quietly most of the time. Imam Ibn al-Qayyim said: “Sometimes the Prophet would recite it aloud, but most of the time he would say it quietly and not aloud.”

Finally, we conclude that it is a Sunnah to recite Al-Faatihah quietly but there is no harm if it is recited aloud sometimes.

Allah knows best.