Check out example codes for "css3 background image curve". It will help you in understanding the concepts better.

Code Example 1

body {
  margin: 0;
  background: red;
}

div#back {
  position: relative;
  height: 200px;
  background-image: url(http://wearepeak.co.uk/wp-content/uploads/2016/02/testimonial.jpg);
  width: 100%;
  border-bottom-left-radius: 70% 60px;
  border-bottom-right-radius: 30% 10px;
}

Learn ReactJs, React Native from akashmittal.com