Error: Reference to undeclared resource with Tier-0 in NSX


I want to apply BFD Settings to my existing Tier-0 Router (deployed with SDDC)
Therefore I want to reference to the existing nsxt_policy_tier0_gateway and add
the resource nsxt_policy_bgp_neighbor where I define the BFD settings.

resource "nsxt_policy_bgp_neighbor" "peering_edge1_seg412" {
  display_name          = "tfbpg"
  description           = "Terraform provisioned BgpNeighborConfig"
  bgp_path              = nsxt_policy_tier0_gateway.t0_test.bgp_config.0.path
  allow_as_in           = false
  graceful_restart_mode = "HELPER_ONLY"
  hold_down_time        = 12
  keep_alive_time       = 4
  neighbor_address      = ""
  password              = var.bgp_password
  remote_as_num         = "4255561896"
  source_addresses      = ["", ""]

  bfd_config {
    enabled  = true
    interval = 500
    multiple = 3

I keep getting this error:

Error: Reference to undeclared resource

on line 80, in resource "nsxt_policy_bgp_neighbor" "peering_edge1_seg412":
80:   bgp_path              = nsxt_policy_tier0_gateway.t0_test.bgp_config.0.path

A managed resource "nsxt_policy_tier0_gateway" "t0_test" has not been declared
in the root module.

I declared the resource:

data "nsxt_policy_tier0_gateway" "t0_test" {
display_name = "t0_test"  

But I think I need to be more specific and point to the section bgp_config within the resource nsxt_policy_tier0_gateway.
Right now I have no real Idea where to start.

The data resource works perfectly fine if I use it as reference if I want to spine up a new
Tier-1 router for example.

Thanks in advance