I have a question on the way we recite Fateha for deceased. Recently a friend who is from another sect raised this question that, where is this teaching of Fateha taken? I did my research but couldn’t find any reference in Quran or hadees. Would you please share some guidance on it?

There are many tradition related to visitation of qabr and recitation of Quran and sending gift to dead one.
Hazrat Isa as was passing from a grave and the person was in azab while he was returning found azab was removed he asked from Allah .
Ya Allah I don’t understand the secret of azab and removal of azab from this person got answer he was a sinful person therefore we punished and Azab stopped because his son recited bismillah .
(Tafseer al Kabeer , Bab e Hadi Ashar vol 1 page 55)
Following is Hadith from prophet saw
Visit graves it reminds you hereafter that means it make a person to prepare for death and fear Allah.

زُورُوا القبورَ فإنها تُذَکِّرُکم الآخِرَةَ…»
Sahib Ibne maja volume 1 page 113
Hadith Narrated by Hazrat Aisha when Rasul asked her to visit grave of Baqee
«فَأمَرَني رَبِّي آتي الْبقِيعَ فَأَسْتَغْفِرَلَهُمْ، قُلْتُ کَيفَ أقُولُ: يا رسول اللَّهَ، قالَ: قُولي: السلامُ علي أهل الدِّيارِ مِنَ الْمُؤمنينَ والمُسْلِمينَ يَرْحمُ اللَّه المُسْتَقْدِمينَ مِنّا وَالمُسْتأخِرينَ وإنَّا إنْ شاءاللَّه بِکُمْ لاحِقونَ
Hazrat Aisha narrated Rasul asked me to do isteghfar
Rasul saw said my Lord commanded me to visit Baqee and seek forgiveness for them (people those who are buried here)
Hazrat Aisha said how do I say oh Messenger of Allah
Rasul saw said
Say May Allah mercy on those who came from among us and those who came later, and In’Sha’Allah we will join you
Sahih Muslim vol 3 page 64
Sahih Nisai vol 4 page 76
Quran is book of shifa and Rahmat therefore best gift is Quran

Holy Quran 17:82
وَنُنَزِّلُ مِنَ الْقُرْآنِ مَا هُوَ شِفَاءٌ وَرَحْمَةٌ لِّلْمُؤْمِنِينَ ۙ وَلَا يَزِيدُ الظَّالِمِينَ إِلَّا خَسَارًا

And We send down of the Qur'an that which is healing and mercy for the believers, but it does not increase the wrongdoers except in loss.

‏Holy Quran 59:10
وَالَّذِينَ جَاءُوا مِن بَعْدِهِمْ يَقُولُونَ رَبَّنَا اغْفِرْ لَنَا وَلِإِخْوَانِنَا الَّذِينَ سَبَقُونَا بِالْإِيمَانِ وَلَا تَجْعَلْ فِي قُلُوبِنَا غِلًّا لِّلَّذِينَ آمَنُوا رَبَّنَا إِنَّكَ رَءُوفٌ رَّحِيمٌ

‏And [there is a share for] those who came after them, saying, "Our Lord, forgive us and our brothers who preceded us in faith and put not in our hearts [any] resentment toward those who have believed. Our Lord, indeed You are Kind and Merciful."

‏Holy Quran 14:41
رَبَّنَا اغْفِرْ لِي وَلِوَالِدَيَّ وَلِلْمُؤْمِنِينَ يَوْمَ يَقُومُ الْحِسَابُ

‏Our Lord, forgive me and my parents and the believers the Day the account is established."
Last if there were not in Quran and ahadith what is better than Quran and recitation of Quran