Is it obligatory to recite Al-Fatihah with deliberation in a silent prayer as in a loud prayer, or is it permissible to recite it quickly? And is it permissible to repeat the prayer if devotion was lost due to the imam's haste?

The worshiper is required to recite Al-Fatiha with deliberation. However, if the congregant knows that his Imam recites it quickly such that he cannot keep up, he should shorten his recitation without compromising the meaning and follow the Imam. Khushu' (devotion/humility) in prayer is a state of the soul from which stillness and humility emerge in the limbs. It is recommended according to the majority of scholars, but not obligatory. As for ṭuma’nīnah (tranquility), it is the settling of the limbs for a period of time, and it is obligatory. The prayer is not to be repeated if the Imam performs ṭuma’nīnah but lacks khushu', because khushu' is neither a condition nor a pillar according to the majority.