To keep the server running always, keep scrolling down on that same medium and look for

Install PM2 on theUbuntu EC2 instance

PM2 is a process runner, basically will keep your API listening even when you end the SSH session with your Ubuntu server

For the second question, there are many ways of accomplishing this CI/CD process: In order of hardest to easiest to set up

1. Configure the AWS CodePipeline with CodeBuild and Code Deploy (hardest to set up)

2. Github actions - setting up so that it deploys and builds the server upon branch update

3. Have a cronjob in the box to pull any changes on every hour, or day. ( easiest to setup )