Need Prestashop expert

I'm a newbie to prestashop and I need someone to help me make some custom mods to Prestashop. The shop will serve different vendors. - Need an entrance page with a warning, only after accepting terms and conditions we'll enter to the shop (This one must be very simple) - Need to sell digital items without having to subscribe or create account - Need to have a backoffice for the sellers have access to their items and get the amount of sold items - Need a box to invite to subscribe to newsletter - Help me in some details like put the banner/logo or other minor details.