Problem with installation Angular 5 and reloading the web page

Question

I installed node.js 8 and then I installed" npm install -g @angular/cli " in command line.
(It's my first time using this framework and actually learning it)
Then "ng new new-app .... and finally created the first app(those files!).
I opened the "localhost:4200" it worked and I went to my project folder, I went to "src/index.html" , changed the title from x to y (for ex.). I saved it.(ctrl +s).
And then when I reloaded the "localhost:4200" it did not change.
Any idea?
Thanks for your time!

Answer 1

How do you run your server?
ng serve?

Answer 2

I once ran it with ng serve -command line and after that, just tried refreshing the browser "localhost:4200". It's kinda complicated for me to understand Angular and Typescript.