Look up Kubler Ross’s stages of grief. It was initially written for people who were terminally ill but it can be applied to most areas of life when we experience grief. It will tell you grief isn’t linear either, but a back & forth through the stages. You also don’t need to forgive them, why would you, instead focus all of your energy on yourself. You can’t control anything about this other than your own emotions, feelings, behaviour etc. Be your best friend & nurture yourself as you move