What is my rightful share of the profit if someone sends goods from outside Egypt for me to sell on their behalf in Egypt for a specified profit?

There is no known limit for profit; rather, it is permissible according to what the seller and buyer agree upon, based on the Prophet, peace and blessings be upon him, saying: "Indeed, selling is by mutual consent."

Considering the questioner as an agent, he may agree with the owner of the merchandise to divide the profit between them in any proportion, or he may agree with him on a specific price that the owner of the merchandise takes, and anything above that belongs to the agent.