I was discussing with a Sunni brother and unfortunately I don’t have the knowledge to reply can you help respond to the below

Hussein (may Allah be pleased with him), the grandchild of the Prophet PBUH, was murdered on the day of Ashura. The *Shias* take this as a day of mourning and beating in order to remember his death and bravery in the face of oppression.
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1) The greatest companion to be killed during the life of the Prophet PBUH was his uncle Hamza. When he saw his torn apart corpse, he cried and said, "I will never face anything more difficult than this! "
However, the Prophet did not take the day of his death as day of mourning or sadness.

2) If there was any sense in what the Shias do on the day of Ashura of weeping and beating themselves, it would be appropriate to do so everyday of the year.
There is no day of the year except that a pious person was killed therein.

3) Ali (the father of Hussein) was killed unjustly and his son lived after him 21 years and did not take the day of his death to mourn.
The Shias themselves do not do the same for Ali as they do for Hussein, even though Ali is of higher status than his son. (May Allah be pleased with them)

In addition can I have Sunni references to the event of kerbala and the breaking of the door on Sayyeda Fatemah as

The tragedy of Imam Hussain (a) is by far the greatest in Islam. Why?
One: he was the very grandson of Prophet Muhammad. He grew up in the lap of the Prophet. The Prophet loved him dearly, and countless Sunni sources confirm his utmost love for him.
1- His own Ummah killed him. That’s more tragic and heart wrenching than Hamza. Hamza was killed by the pagans who were open enemies to Islam. It was an official battle. Imam Hussain was killed by so called Muslims. He did not want to fight. He tried to avoid the battle. They forced him to fight, or he’d pledge allegiance to Yazid. He refused to pay allegiance to the corrupt Yazid.
2- Yes, the tragedy of Imam Ali is great, but no day is like Ashura in Karbala. Not only was Imam Hussain killed, but his infant was slaughtered in his arm. His eldest son was killed. Five of his brothers were killed. 28 of his family members slaughtered. Three days thirsty! His head put on a spear and paraded to Kufa then to Syria. His women and children were chained and taken as captive. When did this happen before Imam Hussain? His tragedy is unmatched!
3- We believe in the Imams of Ahlulbayt, and they said that Karbala is the biggest tragedy. There is a reason why we treat Karbala differently than any other tragedy.

Secondly, the Prophet mourned Hamza and when he saw the people of Medina mourning their dead at Uhud, he said “but my uncle Hamza has no one to mourn him.” So the people of Medina all mourned Hamza.

Third, the Prophet, as mentioned in Sunni hadith, cried for what would happen to Imam Hussain in Karbala many times. At least 12 times as mentioned in Sunni hadith such as Ahmad ibn Hanbal and others. If the Prophet fried frequently for an event that would occur 50 years later, you expect us not to cry excessively for that event? Sunnis today don’t really cry on Imam Hussain. We follow the Prophet’s sunna by crying on him. As for wearing black or hitting the chest, these are ways of showing grief for what happened to him and his family. The Qur’an commands us to love the Ahlulbayt and show it (verse of Mawaddah), and this is one way of showing it.

Sources:

https://www.al-islam.org/shiite-encyclopedia/tragedy-karbala-reported-sunnis-part-1

And the attack on the house of Fatima:

https://www.al-islam.org/shiite-encyclopedia/attacking-house-fatimah-sa

Also see:

http://www.askthesheikh.com/can-you-provide-reliable-shiasunni-sources-on-martyrdom-of-lady-fatima-al-zahra-a-s/