Re replies to your threads, you’ll need to open up the thread to see them. If you click on either ‘new posts’ at the top left hand part of the page, or ‘What’s New’ it’ll bring up all threads that have had any changes still you last looked at them.

Re private messages, at the very top, right hand of the page, you’ll see the ‘notifications’ drop down which will show you the inbox for messages - if you have a message there’ll be a flag on the notification. You can also opt to receive an email when you get a new private message