GitLab - Multiple application servers

I am new to GITLAB and I am working in a firm where currently we are having omnibus Community Edition where all the five GITLAB components like nginx,gitlab-cl,postgres DB ;etc in a single server.

We are now planning to migrate this single server instance to a Multi server combination as 2 App Server - 1 DB server (ref ) for high availability.

We are referring below link for migration by creating backups but we are not able to achive this migration.

I am searching for past one month and still clue less.

please help me on this.Thanks in advance.