al-fatiha

Assalamu alaikum. My question is if one does not have enough time to recite Al-Fatihah during congregational prayer should one bow when the imam says "Allahu akbar?" For example if during the third raka'a of zuhr prayer you have not finished reciting Al-Fatihah and the imam says "Allahu akbar," should you bow or should you finish reciting and then bow? Jazakum Allah khayran.

Assalamu Alaikum My question is about the essence of BismILLAH HirRahman IrRahim when reciting surah Al Fatiha in prayer. Should it be recited aloud or silently? Also, I have heard that if the recitation of Al-Fatiha is incomplete, the prayer is invalid. So, if one forgets to recite BismILLAH HirRahman IrRahim before Al-Fatiha, does this make the prayer invalid? And if one realises that he forgot to say BismILLAH HirRahman IrRahim when he has already started reciting Al Fatiha, should he start Al Fatiha again from the beginning, or re-start his prayer, or carry on as normal? I witnessed a brother reading prayer aloud and he said ?Alhamdulilahi Rabbila alamin? twice, when I asked him why he did this, he said he forgot to say BismILLAH HirRahman IrRahim the first time, so he started the surah again from the beginning. Can you please give us some guidance on this? May Allah reward you.