One thing at a time...
"why I automatic log out and sign in again"| Do you mean, automatically Sign In when you LogOut? Or that you are getting signed out of the forum?
"And the text size is smaller" | Text size is based on Internet Explorer (or your Web Browser)'s viewing Size, if ALL the text is too small, you can go to VIEW>TEXT SIZE then choose an appropriate size. If it is just the Text on your Profile, then go to CUSTOMIZE YOUR PROFILE and increase the text size.
"And ex when I want to go to the general discusion section it goes to DMC4 forums"| I'm not experiencing any problems with the Links...might I suggest Hard Refreshing the page by Holding down CTRL and Pressing F5.
Let me know if this helps...