"I just signed up but I cannot start a new thread, upload an avatar, like posts, etc."
To combat spam and trolls, new members must go through a trial period where they can only reply to existing threads no more than once every 10 minutes. Once 14 days have passed and you accumulate 25 posts and you have received at least 10 likes to your posts, you will then become a member with full privileges. Here are other features you will not be able to do as a new member: post in the Politics subforum, report posts, react to posts, upload avatar, upload attachments, edit signature. You are a full member when you no longer see the "Newbie" banner under your name.