How do you cope with grief when change itself is already overwhelming?

I’m really struggling right now and I don’t know how to process it. A close friend of mine passed away suddenly last week. I’ve dealt with change poorly my whole life, but this… this is on a completely different level. My brain won’t let it go I keep replaying everything, trying to understand what happened, as if understanding it would somehow make it hurt less. I can’t explain my feelings well, so when people ask how I’m doing I just freeze. I’ve had multiple meltdowns this week, and the emotional exhaustion is starting to take a physical toll. I’m eating weirdly, sleeping weirdly, and my routines are all over the place. I don’t know how to get grounded again. Is there an friendly way to cope with grief and sudden loss? What helped you when the world changed faster than you could process it?