Do she like me? what can i do to get her?

Guys, i am 16 years old i am a boy , theres a girl in my cl who i really like i want her to be my girlfriend,she is kinda active type not really shy(but yes sometimes) she is friendly and nice i think she knows that i like her..sometimes i talk to her, play with her.i usually make her laugh. but then sometimes when she sees me she will run away(laughing like its fun).when i ask her to sit next to me she refuses sometimes(many times i asked her for her worksheet to check answers, she would first reject then after a while ask me if i want it). after school she never says bye to me(when going back to home) usually i have to walk to her to say bye. she wouldnt send me txt messages, unless i am the first one to start the sending of messages,i have a feeling that she doesnt really like me but i really need her. i can spend time just thinking about her beautiful smile.today when she was leaving she said bye and said she wanted to take photo, then my friend who was sitting next to me moved away and then she made werid face.so we had to take a group photo me her and him. can anyone tell me why she did this?does that mean she doesnt like me? i m not ugly nor fat. i get top positions in school and also athletics. But i m just a beginner with love. i dont know how to filrt with girls. can anyone please help me out? tell me what i should do? or tell me how i can know what she feels about me?we never hang out except i sit behind her during lesson, we are not even good firends. but i really do love her. how can i tell her that i love her? txt message? or talk to her in real life which one?and can u guys tell me any good way of proposing a girl?i mean how can i say i love you to her?many thanks buddies.****I THINK SHE KNOWS I LIKE HER****CAN ANYONE TELL ME WHAT I CAN TXT HER?LIKE WHAT SHOULD I TALK ABOut WHEN I M TXTING HER?>