Different tasks on our magento shop, build an EBAY API, make website responsive

Hi freelancers, I need an job to be done on our webpage www.skuteri.hr. We have appr. 40.000 articles online, with 1.000 pictures. We will need new features and solutions to make easier work. Our webpage is an online shop for spare parts. We have an list of vehicles (scooters), and on the other hand parts which are connected to one or more scooter types. All parts are in certain categories: cylinder parts, braking parts ec. The vehicles has just two categories: brand and model. Both of them (spare parts and vehicles) are connected with numbers. As spare parts are connected and located with numbers in categories. Quit simple but usefull solution. We import all informations via import excel file where we enter all information's in each product on the page. We have an not too god working export script. What we want is an better way of data import and export or at least the latest version of MAGENTO import/export scripts because the actual one is causing us problems with the re-index and: 1. update our website version of Magento into a current one without loosing the scripts and our customized modules with database's 2. make the webpage responsive and able to be viewed on mobile devices and tablets 3. make an equal page on EBAY as a separate shop 4. build with M2E pro an EBAY API in order to export all our products to EBAY 5. new NEWS module as the old one is customized and ugly and small repair of code for an customized module (ticking clock for sales promotion product) 6. smaller web design & programming changes There are two options to offer your bid. One option is to offer us to rework our old webpage and make all updates, or 2nd option is to offer and bid for a total new approach and new webpage with an similar design which allows us to work as wished. We want avoid entering the whole database once again per hand in the excel file's in order to make it workable with the new online store. Our file's need to be compatible to any reasonable online store which are strong enough to maintain 40.000 and more articles. If you want bid for an new online store, please mention it and offer your price with detail's explaining what exactly you are ready to offer and in which time you would be able to solve. We are ready to accept bids only if the time schedule and whole project would be written down and signed and agreed with penalties in case of delay or wrong functionality.