How can i walk through my API-Gateway? (AKS) - azure

Question

I have an Azure Kubernetes service with currently 3 microservices on it. 1 API gateway and 2 backend microservices. I can address my Api gateway and everything works there. But when I try to address my other microservices via my Api gateway, it still doesn't work.
This is my Yaml file
apiVersion: apps/v1
kind: Deployment
metadata:
name: apigateway-front
spec:
replicas: 1
selector:
matchLabels:
app: apigateway-front
template:
metadata:
labels:
app: apigateway-front
spec:
nodeSelector:
"beta.kubernetes.io/os": linux
containers:
- name: apigateway-front
image: containerregistry.azurecr.io/apigateway:11
resources:
requests:
cpu: 100m
memory: 128Mi
limits:
cpu: 250m
memory: 512Mi
ports:
- containerPort: 8800
name: apigateway
---
apiVersion: v1
kind: Service
metadata:
name: apigateway-front
spec:
type: LoadBalancer
ports:
- port: 8800
selector:
app: apigateway-front
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: contacts-back
spec:
replicas: 1
selector:
matchLabels:
app: contacts-back
template:
metadata:
labels:
app: contacts-back
spec:
nodeSelector:
"beta.kubernetes.io/os": linux
containers:
- name: contacts-back
image: containerregistry.azurecr.io/contacts:12
resources:
requests:
cpu: 100m
memory: 128Mi
limits:
cpu: 250m
memory: 512Mi
ports:
- containerPort: 8100
name: contacts-back
---
apiVersion: v1
kind: Service
metadata:
name: contacts-back
spec:
ports:
- port: 8100
selector:
app: contacts-back
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: templates-back
spec:
replicas: 1
selector:
matchLabels:
app: templates-back
template:
metadata:
labels:
app: templates-back
spec:
nodeSelector:
"beta.kubernetes.io/os": linux
containers:
- name: templates-back
image: containerregistry.azurecr.io/templates:13
resources:
requests:
cpu: 100m
memory: 128Mi
limits:
cpu: 250m
memory: 512Mi
ports:
- containerPort: 8200
name: templates-back
---
apiVersion: v1
kind: Service
metadata:
name: templates-back
spec:
ports:
- port: 8200
selector:
app: templates-back
Do I need an additional Naming Service (Eureka) to access my backend microservices? Or can I do it without.