I'm so very sorry for your loss, and your friend's pain. I lost two people in my life to suicide. I'm 70 years old, and although the feelings I have aren't acute I'm still very sad when I think about this. I really suggest a grief group. Try to find one near you or on zoom. Sometimes funeral homes provide them, or can refer you. Therapy helped me, but grief group the most--it was free and other people understood what I was going through.
As time passed, I was also able to do something in honor of one of my friends that died. She died in part because her family did not take her suffering seriously. Decades later I was able to take care of someone in a deep way. I told my dead friend--I did this for you.
Do you like to write in a journal? It might help to write a letter to your friend. You can't send it in a literal way, but maybe you can find a ritual to communicate your feelings.
Please take care of yourself because grief is a bumpy journey. I'm sure you'll get more helpful response here. Keep in touch.