Suicide certainly can be hard to understand, since it’s not always clear why a person makes this choice.
Many people shy away from the subject, finding it frightening, even impossible to understand.
But you can start by encouraging a suicidal person by brining up the subject.
Say something like, "What you’re feeling sounds really painful and difficult. I’m worried about you, because you’re really important to me. Can I call your therapist for you or help you look for one?”
Reassure them. Remind them of their value and express your opinion that things will improve, but emphasize the importance of seeking professional help.