You could tell them that you understand what they are going through and that they are strong because they were able to go through the struggles by themselves.. basically tell them things that would comfort you if you were in their shoes..

I try to make the person laugh, the learning curve is knowing what's not okay to joke about lol but I've found more often than not you still get a chuckle when you explain how painfully awkward you are 🤣

I have realized I don't prefer people to start out with a joke right away just let them know that you are there and they can talk to you. After that you can just talk and crack some jokes. If you relate to what they are going through that has seemed to help me so I know that someone else has experienced what I am experiencing at the moment. I hope this helps but this is just what I prefer people to do when they comfort me.