Your understanding is great. 1:
For example,I mean :when you bought a book about Chinese learning, your Chinese friend see it , and he or she will ask :"Is that book useful for you to learn Chinese well?,you can answer him or her:有帮助。If you want to emphasize your meanings , you can answer :非常有帮助,it means "very helpful".
The scene emphasize the book is helpful for you.
2:for example, when you reback the book you borrowed from your Chinese friend,your Chinese friend ask you :"is that book useful for you?.You know you don't like the book really ,but you don't have to make your friend angry.you can answer her for the elemental thanks:"有帮助." Don't emphasize it when you get the scene.
If you have any questions,