Why inQURAN does ALLAH say muhammed is too shy to ask you to leave after dinner?

and other persona lmatters of muhammed like.. that he can marry his adopted sons wife or that some people slandered aisha and such personal matters(there are several more) in his personal life..how can that be an eternal holy book for all people for all time if it includes muhammeds personal matters... the reader wont understand what allah is talking about without hadith.... a Christian today reading it would be quite confused as to why they need to know that you shouldnt go to muhammeds house while dinner is prepared and you shouldnt stay after you eat to chat.....?