A sincere question from a Christian - seeking understanding, salam

Assalamu alaykum, I’m a Christian asking respectfully and hoping to learn more about Islam. I have three honest questions I’d appreciate Muslim perspectives on: 1) Why does Islam share many of the same people and tales as Christianity and Judaism but with notable differences? From where I stand, Islam appeared later and presents altered versions of older Biblical narratives. How do Muslims view the relationship between the Quran and the Bible/Torah, and why are there changes in the stories as told in Islam? 2) How do Muslims reconcile the Quran’s emphasis on mercy with violent acts committed by some who call themselves Muslim today? I understand every faith has extremists, Christianity included, but I’m curious how Muslims interpret verses that seem to discuss fighting unbelievers. How are those passages understood alongside the many teachings about compassion and peace? 3) Why do certain Quranic accounts differ from the Biblical versions even though the Bible is older? Stories about Abraham, Jesus, and Moses have overlaps but also clear differences. How do Muslims explain these variations, and what is the Islamic perspective on whether earlier scriptures were preserved or changed? Thank you for any answers or pointers to reliable explanations. I ask with respect and openness.