n - Your project has both `sass` and `node-sass` installed as dependencies, but should only use one or the other. Please remove the `node-sass` dependency from your project. Read more: https://err.sh/next.js/duplicate-sass code example

Example 1: Error: Node Sass version 5.0.0 is incompatible with ^4.0.0.

with npm =>
1.npm uninstall node-sass
2.npm install node-sass@4.14.1
with yarn => 
1.yarn remove node-sass
2.yarn remove node-sass@4.14.1

Example 2: Error: Node Sass version 5.0.0 is incompatible with ^4.0.0.

with npm =>
1. npm uninstall node-sass
2. npm install node-sass@4.14.1
with yarn => 
1. yarn remove node-sass
2. yarn add node-sass@4.14.1

// ^ Update to MR J's post