I want to delete some old posts that I don't want anymore, but there is no button for it. Can any admins out there make a such thing?

There is a delete feature, but it is not currently enabled.  I don't recall ever changing this setting myself, but there may have been several reasons why it was decided not to offer it.  One, deleting replies in the middle of a topic may make the topic difficult to understand, since parts will be missing.  Secondly, even if you posted a topic originally, other members may have responded and they may not want their replies to be deleted.  Lastly, sometimes an offensive message may be posted, reported to us, but then deleted before we have a chance to review it.

Anyway, let me know which messages you would like deleted and why.  You may send them to me by PM if you prefer.