Logic behind Muslim marriages?

The Sunna are very unreliable and I know many Muslims who do not go by them at all. They were written by word-of mouth on top of word of mouth on top of word of mouth. I would just stick to reading the Qur'an to find your answers. It is more reliable than the Sunna. What is in the Sunna is based off of "So and so said that so and so said that so and so said..." You understand what I mean. I'm not being rude, just truthful and they were written hundreds of years after the Prophet died. Tell me who can acurately remember what someone said and then have it passed down accurately throughout hundreds of years?