If it takes the character too many tries to solve the plot, the reader will think the character isn't very bright. Three attempts seems to work well. THEN is a good word to provide the smooth transition from the first to the second attempt at solving the plot. The third and final attempt to solve the plot is the climax of the story, where the main character realizes what she has to do to solve the problem. The third part of the story is the ending, and the ending should be very short.
Stories are more than structure, however.
The next step is to expand your story. You can do this easily by putting a new sentence between each of the previous sentences. Remember that these new sentences must spring naturally from what comes before it. It must be a natural expansion. The expanded story is more interesting than the bare-bones story because it has more details, which allow the reader to better picture what's happening.