This chapter of the guide to Dragon Ball Z: Kakarot has a walkthrough for Easy-Going Genius side quest.
Time frame: From Android Terror Arrives - Episode 2: For the Future to Episode 3: The Training Room's Open!
Reward: 70,842 EXP, 3x D Medal, Card 045, Ultra Brain Bread
Where to start: Western Area, as Gohan.
Dr. Briefs is waiting for you near the fountain. When you start a conversation with him, he will give you a mission.
After that, go to West City.
You must get 3 silver, Densite, and a Skull Robo Gear.
Fly to places marked on the map to get the necessary items. To get parts from robots, you just need to defeat them.
Densite is in the second location marked on the map. All you have to do is fly to this place and then pick up the item.
After collecting all the items, go to the doctor to complete the mission.