How do people talk in group chats?

Ever since I was little, I’ve been extremely shy. I didn’t talk to my classmates and only ever had one or two close friends at a time. When in groups, I used to just shut down and not say anything. It felt like I just didn’t know what to say. Now that I’m less shy, I want to make new friends and join in public chats more but I just don’t know how? Do you just jump straight in and say random things? Talk about myself? I’m so used to replying to a one specific thing a person says that I don’t know how to engage in a conversation with everyone. And if I somehow do manage it, I feel like I have to reply to each person individually, which doesn’t seem to be something people generally do in group chats. Does anyone else get this? I don’t know how people make it look so natural.