I have to finalize manual and automation scenarios and give it the client at the start of the sprint. How to finalize manual and automation scenarios in this scenario.
Note that a test is a performance, not an artifact. One does not "delivers a test".
I can interpret your question in two ways:
1 - An estimation problem: You feel you don't have the tools and skills to understand your scope and grasp an idea of the effort necessary to do a professional job, although probably you can capable of doing the work itself.
2 - A communication problem: You don't have the skill to communicate properly with some person that matters what were the results of your investigations (aka testing).
Any answer to both problems will be: It depends on your context (which we can help if you give more details).
Generally speaking, for starters, I would suggest Bob Martin "Effective Estimation (or: How not to Lie)" talk (here is a nugget of this presentation) for the problem (1) and Michael Bolton's "Breaking the Test Case Addiction" 9-part blog post series, where he talks about the problem of considering tests/testing as artifact generation and alternative way to understand and communicate your testing (as a performance).