How do you forgive your cheating partner?

How do you forgive your boyfriend who emotionally cheated on you (messaged other girls)?

I love him way too much to let him go but he's been lying and cheating on me.

How do we work through this? How am I supposed to trust him and believe anything he says now? All my trust for him is gone because he has lied to me way too much.

I want him to change and be a better person. How do we do that?