Is it permissible to work on designing a PowerPoint presentation for a company that offers an application based on a cash-back and cash-referral system, where the company gets a percentage of the discount granted by the restaurant, and a portion of this percentage goes to the buyer as cash back, another portion to the company as profit, and a portion to the users' invitees as cash referral?

There is no objection to the company contracting with restaurants and shops to advertise on its application in exchange for a discount percentage, part of which is distributed to the company, part to the buyer through the application, and part to those who invite others. This discount is a fee for advertising, and the preponderant opinion is that it is permissible for the fee to be a percentage of sales. There is no objection to giving a discount to someone who invites others to use the application if the application's use is free. However, if one pays money to subscribe to the application hoping to get a discount by inviting others, this is prohibited gambling. It is permissible to create a PowerPoint presentation for the company if the contract is permissible, because it is an aid to a permissible act.