Starting React App from pulled github project - node.js

Question

I've pulled a github repository containing code for a reactjs app into one of my directories but I can't find a way to run the app on my computer. I can start a new app using create-react-app but I can't/(don't know how to) use the existing app for instead ofa freshly created one.
I'm running Ubuntu 16.04.3 on a virtual machine, my node version is 4.2.6.
I've tried sudo apt-get install --only-upgrade nodejs but it simply says my node version is already up to date. (I include this because npm start gives me a bunch of errors and tells me that it may be because I might have to update node) but the app I create with create-react-app works fine?
The error:
Package.json:
{
"name": "my-app",
"version": "0.1.0",
"private": true,
"dependencies": {
"bootstrap": "^3.3.7",
"express": "^4.16.2",
"package.json": "^2.0.1",
"prop-types": "^15.6.0",
"react": "^16.0.0",
"react-bootstrap": "^0.31.5",
"react-dom": "^16.0.0",
"react-router-dom": "^4.2.2",
"react-scripts": "1.0.14",
"uuid": "^3.1.0",
"webpack": "^3.8.1"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test --env=jsdom",
"eject": "react-scripts eject"
},
"devDependencies": {
"babel-cli": "^6.26.0",
"babel-preset-env": "^1.6.1"
}
}

Answer 1

Carry out the following steps:
//Step 1:
git clone [repository url]
//Step 2:
cd [local repository]
//Step 3:
//Check package.json file and ensure scripts are notated as below:
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},
//Step 4:
/* Delete the node_modules folder and any 'lock' files such as
yarn.lock or package-lock.json if present.*/
//Step 5:
npm install
//Step 6:
npm start
To Note: There can be some conflict between yarn and npm when cloning from certain repositories. It's best to assume that every repo may need trimming before ultimately running npm install. I tested the above steps several times under several different factors. This is the best I have so far.

Answer 2

In case of issues shown after npm install, run the below to automatically fix the issues:
npm audit fix
Alternatively, use the below to see the errors:
npm audit