Can you guys share me your experience on setting up the deadlines, sprint plans, story points and how you dealt with the new requirements which will bring you potential big clients but has to be done in impossible deadlines.
Does startups commonly release new features from writing a MRD to production release in just three days of deadline?
Then promise to deliver some value. Where some value is the core features + some of the nice to haves. Promising or even trying to deliver a fully fixed set of features on a specific date almost never works in software development. Issues always evolved while doing the work. So plan on using a team lead who manages the project and sharp shoots issues with the dev team through paired programming. DO NOT PLAN on your lead having full development capacity. They will need to commit to other business activities to keep things moving.
Avoid over architecting the solution up front. Find the simplest value adding feature and work from there letting your design evolve. Back up your development efforts with TDD. And engage with the client / product owner often. This means frequent releases and meetings.
And at the end of the day delivering some value the client / product owner can leverage allows them to keep moving their objectives forward while the dev team evolves it understanding of the domain and challenges related to the project.
Finally, do not be afraid to say NO. If you feel it is unreasonable then say so. Avoid taking on work with insane deadlines no matter how important / critical it seems. Make a plan to work around the issue in a reasonable manor. Hopefully by continuously engaging with key stake holders issues are raised early and handled in a sustainable manor.