What is the point the author is trying to make in "Kew Gardens"?
The eNotes study guide has a good discussion of the themes in this story. Those themes include loneliness and alienation, gender roles, and nature.
It's not surprising that you're having difficulty with the story. Woolf's style of writing in stream of consciousness can be difficult to follow. One other complication with "Kew Gardens" is that it is not a typical short story, with a beginning, middle, and end. The typical short story elements (rising action, climax, denouement) are missing as well. The story is just a series of vignettes set in a park.
Maybe it will help if you put yourself in the narrator's place. Imagine that you are sitting on a bench in Kew Gardens (which is a park in London). You alternate between watching the snail make its progress along the leaf and listening to snippets of conversation of the people who pass by. Perhaps that will help you to grasp what Woolf was trying to do.
Another way to think of the story is to imagine it as an Impressionistic painting. Just as artists used little dots of paint to depict a scene, so also Woolf is using little bits of conversation to depict the action.