Is a SSTP-VPN connection enough to hide my internet traffic?
I am currently renting an apartment with shared guest internet and I don't have access to the router. For several reasons (mostly privacy), I don't want others in my apartment to see what I am doing online.
- Is it possible for other people (in my apartment and network provider) to see what I am doing online when I have SSTP-vpn enabled?
It's not "impossible" only unlikely (time best spent elsewhere, if they have the technology).
It's possible to have Deep Content Inspection and your ISP almost certainly has Deep Packed Inspection. You can buy a box like the Cisco SSL Appliance it allows "Decryption of traffic up to 3.5 Gbps with over five million simultaneous flows" and permits "Logging the details of all SSL flows to detect suspicious trends or patterns".

There's a good chance that your roommate doesn't own one, there's an excellent chance that your government has much better equipment. You can build your own box, it's just a computer with a couple of ethernet ports, and there's software available. Since SSTP is proprietary you won't find people publically advertising that they're selling equipment that's not licensed and if there's a court order for lawful interception it's not helpful to announce the availability and usage of such equipment.
- Do I need to do extra steps to enhance my privacy at home?
Against your roommate?, probably not.
The usual rule applies: Don't have or do anything you don't want anyone to know about.