Turnkey online learning platform (LMS)

We are launching an educational project and are looking for a developer to build a complete online learning platform. At the core of the system is a course catalogue, where every course is split into modules and individual lessons that combine video, text and downloadable materials. Learners move through the lessons in order, and after each block they take quizzes that are graded automatically with a running score. The platform must track progress for every user: which lessons are finished, how many attempts each quiz took and the average result achieved. When a course is completed, the system should issue a personalised PDF certificate that can be downloaded and verified by a unique number. Instructors need a comfortable dashboard to upload materials, edit lessons and review reports for their groups. Analytics matter to us as well: student activity, weak topics and completion rates. We expect a responsive interface for phones and tablets, separate roles for administrator, curator and student, and reminders about deadlines. Please send proposals describing your experience with similar projects, your technology stack and a rough estimate of the timeline and budget.