This chapter of the guide to Dragon Ball Z: Kakarot has a walkthrough for the Like a Different Person side quest.
Time frame: From Evil Emperor Frieza - Episode 7: Bulma's Advice to Episode 7: Interplanetary Preps
Reward: 5,292 EXP, D Medal, 2x Rose Wheat, 2x Gelatinous Egg
Where to start: Southeastern mountains, as Gohan.
Ox King stands in front of Gohan's house. Talk to him to get the mission. Your first task is to go to your mother and talk with her. After that, go back to the man. He will give you a list of ingredients that you should bring.
Your task is to collect 4 carrots and 2 pieces of meat. Carrots can be collected from the farm or they can be purchased.
To get the meat, you need to kill a gazelle. They run in open green areas.
When you get home, ask your mother to make dinner - this will finish the mission.