Best way to get over a girl?

Give your brain something new and interesting to distract. You may join gym or some fitness class . This helps in letting out that emotional built up. This way you become a better versions of yourself.
Start reading some books--I would recommend The Game of Life and How to Play It, published in 1925. There is an audiobook for that available on youtube. You can start following new topics.
For example I recently stared following the guns channels on youtube. They explain how different guns work and their advantages and limitations.
I mean to say just give your brain something new and interesting and in no time you wont remember the girl.