Why can't i reply to other peoples threads?
You can reply, but you can only reply (and post) in the Newbie forum. This is because you are a newbie. Try reading the NEWBIE README thread that is pinned to the top of the Newbie forum, it will likely answer many of your questions.
I have to make my own in order to become a Jr.Members.
You have to either create a new post
or reply to an existing post in the Newbie forum before you become a Jr. Member.
This is so stupid,
No. It isn't.
how can i fix this?
You can't.