[vayarajesh]

I started using bootstrap from Bootstrap 1 and it was not difficult to start using 2 or 3 - the basic conceptual framework remains almost the same and most of the implementation anyway requires the Bootstrap documentation open on the side for reference.

However, I would recommend to move away from Bootstrap to Material design for example, I feel (after using both) Material design is more well though framework and it also has bindings with Angular (that is if you are building angular apps) through [angular-material](https://material.angularjs.org/latest/). There is also standalone framework [getmdl.io](https://getmdl.io/started)

Then there is a very detail documentation on how to think like [Material design](https://material.google.com/) way by Google . Checkout the components section from the menu, it is really nice they way explain the theory behind why each component the way it is