How to Install and Use Docker on Ubuntu 18.04

sudo apt update
sudo apt install apt-transport-https ca-certificates curl gnupg-agent software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
sudo apt update
sudo apt install docker-ce
sudo apt install docker-ce=5:18.09.6~3-0~ubuntu-bionic
sudo apt-mark hold docker-ce
sudo systemctl status docker
sudo usermod -aG docker $USER
docker container run hello-world

How to Install Git on Ubuntu 18.04

sudo apt update
sudo apt install git
git --version

How to Install and Use Docker Compose on Ubuntu 18.04

sudo curl -L "https://github.com/docker/compose/releases/download/1.23.1/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose
docker-compose --version