I have to finalize manual and automation scenarios and give it to 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 are 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 the results of your investigations were (aka testing).
An 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 ways to understand and communicate your testing (as a performance).