How to completly remove HTC ONE M8 operating system from

[AC Question]

My HTC one m8 has been acting up for months. It would say " This process stopped working or it crashed" and it would keep say infintily . So i factory reset it twice and it would work fine but super slow . I checked the the memory usage and android os is using like more than half of my memory ( 1.8). I tried clearing the cache and factory resetting and resetiing cache partition and nothing helped. Now i want to take it a step further and remove the entire os and freshly reinstall the entire firmware. How would i go about doing that without bricking the phone?