I always failed to update firmware use my smartphone to my mavic air, anybody can help me please, until now I am to scare try to flying my mavic, thx

Try to update your Mavic Air using the DJI Assistant on your computer.   You can get the DJI Assistant here.

Yeah, use version 1.2.4 of DJI Assistant 2 for FW updates.

Hi, I'm sorry to hear about the issue, please follow the tutorial video below to update the firmware via DJI assistant2, hope this can help. Thanks.

I have the same issue with the smart gesture mode sign grayed out, but I figured it out by reinstalling the DJI assistant 2 and making sure clean up the DJI Assiatant 2 for Mavic installation packages if you by chance installed both. The later one is for Mavic 2 not for Mavic Air. It woks on my Mac book lap installation with the Mavic Air aircraft.
Hopefully it helps.