Failed Auto Take Off - Beginner asking for help - Logs

Hi All

I’m new to Ardupilot and rc planes altogether and would really appreciate your help.

On the second successful flight of my twin tractor plane(believer), I attempted to use the auto take off feature but the plane slowly went down to the ground instead of climbing up. I’m still in very early stages of understanding how to read logs and would really appreciate if someone can have a look at the log from the flight: https://1drv.ms/f/s!AsR_nLEWilXTgZxwuJ0oAz4eK4di4A

Also if there is something else wrong in the settings, please point it out to me.

Thanks in advance!
Evgeni