how to draw shapes in background in html+css?

I love learning by doing , the challenges at Frontendmentor.io are great help.

I want to know how to create those blue shapes (in top section and bookmark_in_one_Click section) behind the images,(yes those shapes are separate from images); I guess it might be something to do with SVG but I am not sure how and can't find any useful link on google. Any article/tutorial/code example would be great help.