Customize wordpress website -- 2

Hi , I have a website ready , but I need to do some changes on it to make it professional and ready to use 100% the website is ; [login to view URL] - I need to make a buttons on the top for login and logout , dashboard for seller , - I need to make chat for each seller ( multiple vendor like fiverr website ) and notifications - I need to configure the gateway payment ( already installed ) I have already digital downloads plugins ready but I need to configure it professionally , - I need to handle the sliderevolution to be more professional , - I need handle the files to be saved on cloud AMAZON - I need to manage mail chimps for marketing and sending emails . in Brief I need my website to be a professional website please let me know the cost and the time