I just will describe how it configured on my side. I've installed cert-manger on my Kubernetes by using this tutorial :

https://docs.cert-manager.io/en/latest/getting-started/install/kubernetes.html

I've checked is it installed and it is :

Also I have ingress-resource with the next config:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  annotations:
    certmanager.k8s.io/acme-http01-edit-in-place: "true"
    certmanager.k8s.io/cluster-issuer: letsencrypt-issuer
    kubernetes.io/ingress.class: nginx
    nginx.ingress.kubernetes.io/from-to-www-redirect: "true"
    nginx.ingress.kubernetes.io/rewrite-target: /$1
  name: boonotes-ingress-resource
  namespace: default
spec:
  rules:
  - host: www.bnsfun.com
    http:
      paths:
      - backend:
          serviceName: booknotes-front-end-service
          servicePort: 80
        path: /?(.*)
  - host: www.bnsfun.com
    http:
      paths:
      - backend:
          serviceName: booknotes-back-end-service
          servicePort: 3000
        path: /api/?(.*)
  tls:
  - hosts:
    - www.bnsfun.com
    secretName: letsencrypt-certs
status:
  loadBalancer:
    ingress:
    - ip: some ip

Also, I've configured the certificate :

kubectl describe certificate booknotes-certificate

Name:         booknotes-certificate
Namespace:    default
Labels:       <none>
Annotations:  kubectl.kubernetes.io/last-applied-configuration:
                {"apiVersion":"certmanager.k8s.io/v1alpha1","kind":"Certificate","metadata":{"annotations":{},"name":"booknotes-certificate","namespace":"...
API Version:  certmanager.k8s.io/v1alpha1
Kind:         Certificate
Metadata:
  Creation Timestamp:  2019-11-17T04:51:57Z
  Generation:          2
  Resource Version:    7257970
  Self Link:           /apis/certmanager.k8s.io/v1alpha1/namespaces/default/certificates/booknotes-certificate
  UID:                 fbe1d9c0-08f5-11ea-82b3-42010a80017a
Spec:
  Acme:
    Config:
      Domains:
        www.bnsfun.com
      http01:
        Ingress:  boonotes-ingress-resource
  Common Name:    www.bnsfun.com
  Dns Names:
    www.bnsfun.com
  Issuer Ref:
    Kind:       ClusterIssuer
    Name:       letsencrypt-issuer
  Secret Name:  letsencrypt-certs
Events:         <none>

I've also created a secret:

Here is my sevice & ingress section:

I've used this tutorial to configure it : https://medium.com/@betandr/kubernetes-ingress-with-tls-on-gke-744efd37e49e

and official documentation of cert-manager to install cert managed. What do I wrong? How can I check why this doesn't work? I've tried a lot of stuff, but all doesn't work for me. For sure I do something wrong. But what? I've understood that I need cert-manager for updating my lets-encrypt certificate, also I need to create secret to store it, then I need configure my ingress in tls and annotaions. Pls could you help me to find out more what should happen there and what are the main steps to complete it? If you need more info , pls let me know

Here is my issuer:

apiVersion: certmanager.k8s.io/v1alpha1
kind: ClusterIssuer
metadata:
  name: letsencrypt-issuer
spec:
  acme:
    email: email
    http01: {}
    privateKeySecretRef:
      name: letsencrypt
    server: "https://acme-v02.api.letsencrypt.org/directory"