Assalamu-Alaikum, It is said somewhere that Allah(SWT) will save Quran and its authentication.But, I have read many stories and histories about our Prophet(PBUH). But how authentic those are? How to know if those are authentic?
There are things known as Hadiths which are a collection of things the prophet used to say. The most known Hadiths and ones that are most reliable are found in Sahih Bukhari and the one after would be Sahih Muslim. These are books which contain different hadiths about the prophet.
Another thing that links to these hadiths are the sunnah which are acts of the prophet. These acts are written in different Hadiths. The sunnah contains words and acts from the prophet and you can also find these located in Sahih Bukhari and Sahih Muslim.