Modification and optimization of website (PHP+HTML) -- 2

I have a website developed on PHP in HTML5, some pages WP, Plateform codeigniter, where I need to make some modification : 101 tasks : the tasks are divided for its role in the site, i.e. on a coding linked on 3 pages, there are 3 tasks, fix bugs, add options and make changes to the coding already done, also add integrate Ingénico payment API, this is how the tasks are cut - Design 25 tasks - quick modifications 29 tasks - modification technique 7 tasks - modification complex 40 tasks the tasks are in Jira, and access to source code in gitlab, project manager and myself to communicate and have more information, working time 15 -20 days in : 5 milestones, I realize milestone once work done and test done. time working : each milestone will last 3 – 4 days once the milestone is finished, and the test is successful, I realize the milestone and I will pay for the next milestone If one of the milestones is late, this does not guarantee the continuation of our agreement milestone 5 is for testing all work done by you and support me set your own price and the most suitable offer will be accepted