Classmate claims the Islam is the most peaceful religion. How do I debunk that?

My classmate argues that women are treated equally to men in Islam and that the Quran does not forbid women from working or require them to stay at home. He also claims that the Quran has made scientific predictions, such as the Big Bang, which were only discovered later by science.

I don’t know much about Islam, but he insists it’s a peaceful religion. When I asked about women and the people who face oppression or suffer from religious trauma, he said those people aren’t practicing the religion the “right” way.

This made me wonder: what exactly is the “right” way to practice Islam? Considering how diverse... isn’t it impossible for all Muslims to agree on a single “correct” interpretation? How does he know what the right way is? Does he mean he agrees with every single thing that is written in the Quaran?

Edit: let's take homesexuality as an example. It's scientifically proven that homesexuality is valid just as heterosexuality. None of the religions have figured that out/predicted that.