This chapter of the guide to Dragon Ball Z: Kakarot has a walkthrough for the Rouge Chef Melone side quest.
Time frame: From Evil Emperor Frieza - Episode 6: The Magic Words - Episode 6: The Fearsome Emperor
Reward: 23,144 EXP, D Medal, Improved Scouter
Where to start: Planet Namek, as Gohan.
This quest begins with a fight with a Frieza soldier. He has a lower level than you, so this enemy shouldn't give you any trouble.
Your next task is to get Yuckermelon, Ajisa Orange, and Rollonut. All items are located in the places indicated on the map. All you have to do is fly there and collect the light purple orbs.
The task will end after a short conversation with the soldier.