As mentioned in the project description, those could be on behalf of yourself or someone else. Keep in mind that in order for this to be a successful project, your chosen topic cannot be either too simple (or you'll have not much to write about) or too complicated (or you will not be able to complete it by deadline).
For this homework, you should write a potential negotiation. Some possibilities include (but are not limited to) the following:
Negotiating a purchase—for example, a TV, car, computer.
A competition in which all members or subsets of members strive to see who can get the best deal on their cell phones, credit card rates, or “flea market” purchases.
Negotiation (or re-negotiation) of lease agreements, partnerships, or contracts.
Negotiation of reimbursements for poor service or resolving customer service complaints.
Negotiations for events such as weddings, group travel plans, class gatherings, etc.
Negotiating discounts with local businesses for student groups, clubs, etc., including for discounts on treats or benefits.
Negotiating with friends/family members to resolve disagreements or disputes (e.g., vacation locations, long-standing conflicts).