General Issue

Hey all,
i’m complete new to the Router OS and i bought a RB2011L-IN to create a PPTP Tunnel to a provider for routing External IPS to my network.
I’m using a DSL with Dynamic IP and that’s the reason why i’m using this.
Now i have a general issue.
Setup currently: Fritz box ↔ Forefront TMG ↔ Clients(Server)
what i want to do is still use the AVM FritzBox for internet access but the RB behind to route all the traffic and then connect to the Forefront System.
In general i don’t have any clue how to realize this.
Do i need two interfaces from the RB one to the fritzbox the other to the TMG Server or is one sufficient enough.
Also the RB should create a PPTP Tunnel to vollmar.net who is providing the Fixed IP’s. (You’re getting there 8 public ip’s routed through the PPTP Interface)

Any help is really appreciated. Sorry for the stupid question but i don’t have any clue at the moment and trying everything since 2 days

Thanks in advance