Help with pfsense in proxmox with 1 nic

Hi,
this guide (not read in detail) does not use a PFSense. It youse the Proxmx VE internal Firewall with NAT.
Here in the forum are quite a lot of such setups that you like to achieve.
Search for "PFSense ovh"

You need two bridges one for the WAN port in the PFSense and one for Internal VM/CT communication.
WAN <-> vmbr0 (PVE) <-> vtnet0 (PFSense) <-> vtnet1 (PFSense) <-> vmbr1 (PVE)