How many personnel roles are there in the SAP project?

1. Ordering stage: At this stage, sales and presale work together to understand the business needs and come up with preliminary suggestions for customers. Then there are the following questions: 1) What are the possible roles at this stage? Besides the sale and presale I mentioned, is there anyone else? For example, a business expert, someone who is familiar with the business? 2) Or the project manager who may be arranged later also needs to be involved? 3) Also, who should make the plans and estimates of manpower and space? If it is done by presale, then if the project really goes ahead, but the project may not be done by this group of people who placed orders, what should I do if the project manager does not approve of the plan and the man-day estimate? 4) Will there be dedicated people doing presale? Or does the presale have to come from the implementation team? One difficulty I am currently encountering is that since the company is an independent consulting company under the group, its current business is mainly based on the needs of the group. There was no single-playing stage before. But in order to adapt to later external development, this process is needed. But at this stage, for those who will implement the project in the future, they believe that the previous research, plan or estimate should be done by the same group of people, otherwise they will not recognize it. This is a contradiction. 2. Project implementation: from the end of the order to the formal establishment of the project, the beginning of organizing project personnel to station in the project, and the completion of the entire project implementation. There are several questions: 1) What are the personnel roles in the entire project implementation process? In addition to the implementation consultants for each module, there may also be development ABAP consultants and basis consultants. What other roles can be assigned to the project team at different stages? 2) Will there be a role of business consultants in SAP implementation projects? Are they people who may not necessarily understand system implementation, but may be familiar with business processes? If there is such a role, what is his position in the project? What responsibilities? What stages do I need to participate in? What is the relationship like with the implementation consultant? These questions really confuse me. I hope everyone can give me some advice and share their experiences. Thank you! !