من هو الحاكم المسلم الذي فتح القدس أولاً؟

That is correct. Caliph Umar ibn al-Khattab entered Jerusalem in 638 CE (15 AH), marking the beginning of Muslim rule over the city. Following the conquest, Umar issued the Covenant of Umar, a guarantee of safety for the city's Christian residents and their places of worship, and he cleared the Temple Mount (Al-Haram al-Sharif), which had been left neglected, to establish a place of prayer that would later see the construction of the Al-Aqsa Mosque and the Dome of the Rock under the Umayyad dynasty.