Hi everyone!
I am pretty new to Roots technologies, forgive me for the stupid question.
I am using Bedrock and Sage on my first project. I am on an iMac running MAMP 7.2.
Using yarn dev as explained here automatically crashes my entire local server.
All pages and sites that I run locally (event those not running bedrock and sage) return the same message:
Cannot GET /path/to/site
Same for PHP My admin
All goes back to normal after killing yarn dev process.
yarn build works fine interestingly.
Please let me know if there is any hope 
Thanks all for your support.