I´m currently learning much about VPN security and now I got to that point where I would like to know how a VPN provider is able to hide my traffic from other user. I am connected to one gateway (as others user) and if I use it with http websites my requests are transported in plaintext. Why are other users not possible to intercept my traffic if we are on the same VPN?. I think I am missing something now. Can you lead me in the right direction?
Other clients on the same VPN service don't share your tunnel to the VPN. Your connection to the VPN is encrypted with a key that is only used for your communication.
After your traffic reaches the VPN, it is no longer encrypted by the VPN tunnel. The traffic (in your case a plain text HTTP request) is forwarded to the host you're trying to talk to (example.com).
The hosts response is then returned to the VPN and returned to you over the VPN tunnel.
For economic reasons (and potentially some anonymity) many VPNs use shared IPs. This means many users traffic is sent from the same IP address. Even in this case, other users can't intercept your traffic.
Essentially VPN users are just trusting a third party to forward traffic in their behalf. Even though you may see a private IP on your system, traffic from private IP to private IP (VPN user to VPN user) is typically disabled on most VPNs (although there are some setups where that is the purpose of the VPN)