After 01
Calendar invite
Google sends a confirmation email with a Google Meet link. The invite shows up in your calendar, in the time zone you booked it from.
After 02
One paragraph
Reply to the invite with one paragraph about the system, the deadline, and the constraints. That is the agenda.
After 03
Fixed price, in writing
If there is a fit, you get a written spec and one fixed price. If there is not, you leave with names of people who can help.