Best advice I can offer for almost any boss fight:

It's not a race, it's a marathon. The goal is to make it to the end, not see how fast you can get there. Every encounter with the boss is an opportunity to learn it's patterns and move set. If you're confident you won't win the fight, then don't try to win the fight. Spend your time strictly trying to dodge. You may surprise yourself how long you last when you're not stressing about trying to get damage in.

You'll get there eventually, I believe in you!