1× F450 Quadcopter Drone frame With Integrated
PCB
1× FlySky FS-i6s 2.4G 10CH Radio Transmitter
With FS-A10b 10CH Receiver
1× 1000KV A2212/13T Brushless Motor With Bullet
Connector for Multirotor & RC Plane (Set of 4)
1× Simonk 30A 2-3s Brushless ESC With T Plug Connector for Multirotor & RC Plane (Set Of 4)
1× 1045 Carbon Nylon CW/CCW Propeller for Multirotor & RC Plane (2 Pair)
1× DJI NAZA M Lite Flight Controller Without GPS
For Drone
1× XT60 Male Connector With 9cm 14AWG Silicon
Wire

I am very beginner and this kit is offered by company 18k
And I don't know which battery to buy and how much mah would give me 18-20 mint flight time tbh I am just building this drone for fun but I really want more fly time I have seen drones flying around 20 min but they didn't mentioned what parts they used please help me 🙏🥹

Use atleast 4000mh battery to reach your mentioned flying time and reduce the size of propeller.