[HELP!] Reading logs-PID and loiter mode not very stable

We are beginners with the ardupilot. we have come to the point at which our drone somehow can hold it in loiter mode and can do auto in very low speeds (though it could hold its own for a while against strong wind). if we speed it up it becomes erratic. We have the log files we can see the data but we really dont understand much. can you help us better tune this bad boy?

we have included the log file and auto analysis results for a several takeoffs.

log file: https://goo.gl/JWdrAu

`Log File C:\Users\hp1\Documents\Mission Planner\logs\QUADROTOR\1\2017-06-28 20-57-09.log
Size (kb) 7566.3681640625
No of lines 91153
Duration 0:16:30
Vehicletype ArduCopter
Firmware Version V3.4.6
Firmware Hash 5221448a
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = NA -
Test: Brownout = GOOD -
Test: Compass = GOOD - mag_field interference within limits (23.94%)

Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = GOOD -
Test: GPS = GOOD -
Test: IMU Mismatch = NA -
Test: Motor Balance = WARN - Motor channel averages = [1467, 1346, 1368, 1451]
Average motor output = 1408
Difference between min and max motor averages = 121
Test: Parameters = GOOD -
Test: PM = NA -
Test: Pitch/Roll = NA -
Test: Thrust = NA -
Test: VCC = UNKNOWN - No CURR log data

Thanks for your responses, RT team.