How to run bash commands from yml after creating ubuntu registry via docker?

So I made a ubuntu docker registry with all the necessary packages and programs installed.

My yml file:

image: registry.gitlab.com/guavaman791/testing:ubuntu

stages:

  • build

Build My App:
stage: build
script:
- apt-get update
- apt-get install -y git
- ec -version
- python3.7 -version
- echo “hi”

It throws command not found bash: line 91: python3.7: command not found. Same thing with other commands such as ls or cd