update cart quantity automaticly when writing new value

when adding an item to cart, then go to the cart page, the default value is one
but when I am trying to change value = 1, to value = 5 (as an example ) and press enter
the page refresh and value still one.
the only way to change value is to click on the "+" button, and even if u click on "+" the quantity increases one and the page refreshing
so you cant increase in the as much as you want. so how i can resolve this problem :
- write the quantity that I want and update it automatically.
- Click on + button to change the quantity without refreshing the page in each time i click on "+"

please i want your help because this problem makes disaster on my website.

better ask the people you got the template from.