how to seperate and show each forum on its own page?

You don't need different pages. All forums can be on the same page by only visible for certain Users/Usergroups. For Example:

If you have two forums (cat, forum or subforum), say Class Forum 1 and Class Forum 2 and two users Student 1 and Student 2. You can do this configuration to make a user specific access forums:

1. Create a Class Usergroup 1 Usergroup and attach User 1 to this group (Dashboard > Forums > Usergroup)

2. Create a Class Usergroup 2 Usergroup and attach User 2 to this group (Dashboard > Forums > Usergroup)

3. Navigate to Dashboard > Forums > Forums. Edit Class Forum 1 and set permissions:

• Admin - Full Access
• Moderator - Moderator
• Customer - No Access
• Registered No Access
• Guests - No access
• Class Usergroup 1 - Standard Access
• Class Usergroup 2 - No Access

4. Edit Class Forum 2 and set permissions:

• Admin - Full Access
• Moderator - Moderator
• Customer - No Access
• Registered No Access
• Guests - No access
• Class Usergroup 1 - No Access
• Class Usergroup 2 - Standard Access

Thank you vary much for the quick answer!

Is there any way to automate the process of attaching students to their usergroup? maybe by choosing wich class they are part of while register?

or the only way is to add each student manualy using the dashboard?

You do Usergroup - Forum Access - Forum configuration one time. But each registered user should be manually attached to correct usergroup. You just need to edit new user and change the Usergroup, all other configurations will be applied to this user automatically.

ok thanks a lot !