i just paid and download minecraft but i cant play ... it says "crash" .. i need your help please... sorry for my english i am from greece

i installed minecraft....
minecraft launcher 1.6.70
i downloaded from https://minecraft.net/en/download/
i payed with paypall ... i dont know the problem ... maybe my pc is too old for the game... also my english is not good...
maybe can u help me fix it step by step
maybe i cant play in my pc u can give me my money back.
Thank you