This is a pipeline that worked for me on bitbucket.For ftp i didnt add public folder to the host name it just worked still

bitbucket-pipelines.yml

image: vesica/php73

pipelines:
  default:
    - step:
        deployment: production
        caches:
          - composer
        script:
          - apt-get update
          - apt-get -qq install git-ftp
          - git ftp init -u "$FTP_USER" -p "$FTP_PASSWORD" ftp://$FTP_HOST