What helps
Listen more than you advise. Ask, do not assume. Reflect back what you heard. Use their name. Sit with silence. Ask directly about safety if you are worried: "Are you thinking about suicide?" — research is clear that asking does not plant the idea.
What does not
Toxic positivity ("everything happens for a reason"). Comparing pain. Trying to fix. Pushing solutions before they feel heard. Disappearing after one big conversation.
Looking after yourself
Supporting someone in distress is heavy. Set limits, keep your own routines, get your own support, and know when to involve their GP, family, or emergency services.