Q- Is it true that Jibrail (‘alayhis salam) taught the du’a ‘Ganjul ‘Arsh’ to Nabi (sallallahu ‘alayhi wa sallam) and that whoever recites it no enemy will be able to overcome him?
Have not come across any such detail about this du’a in the reliable books of Hadith.
Mufti Mahmudul Hasan Gangohi (rahimahullah) writes: ‘There is no authentic (sahih) chain for this [du’a]. The merits that are written for [this du’a] have no basis. Instead of reciting such passages, one should rather engage in Quran recital, sending salutations upon Nabi (sallallahu’alayhi wasallam) and istighfar.’ (Fatawa Mahmudiyyah, vol.5 pg.347. Also see Fatawa Rahimiyyah, vol.2 Pg.245-246)
Dua-e-Noor, Dua-e-Ganjul Arsh and Dua-e-Jamilah are not proved from Hadith but they are correct as per the meaning and context, hence if someone recites them it is allowable. But the so-called virtues and merits of it are not proved from hadith
And Allah Ta’ala Knows best
https://hadithanswers.com/an-unauthentic-dua-dua-ganjul-arsh/
https://darulifta-deoband.com/home/en/Death--Funeral/33267
https://islamqa.info/en/answers/27237/is-there-such-a-thing-as-duaa-kanz-il-arsh
https://mawdu.wordpress.com/2012/12/01/dua-ganjul-arsh-source-authenticity-from-hadeeth-fabricated/