Modifications for a Dutch Magento webshop

We need a few modifications for our Dutch webshop. Because the webshop is live you cannot work on live solution, first you need to install the webshop on your own server and make all changes there. After that we agreed that all changes are solved good then all changed files need to be uploaded to current website. So not replace a total backup, because otherwise we loose important data. All changes should work good in all browsers! We are looking for a freelancer who has a lot of experience with Magento. We also want a longterm business relationship for further projects. If you can do this project, please give us your bid and tell us in how many days you can finish it? Please only place a bid if you are 100% sure you can fix all issues 100% good! The project description and details you can find in attachment '[login to view URL]'.