Fcpx : My motorized slider it’s ruining my audios

You could try the Voice Memos app on your phone to record the audio. It's just audio so files will be much smaller. Make sure you clap in front of the camera where both the camera and the iPhone can hear it so you can sync them up in FCP. You will probably need to convert the Voice Memos mp3 or aac file into a 48kHz wav file using something like the free Audacity before importing into FCP.

How are you capturing the audio for your videos?

If the camera is mounted on a slider, the mic from the camera is very close to it.

If you can record audio with, for example, audio recorders with lavalier microphones, you can then synchronize that audio in FCP and turn off the audio from the camera. That should produce much better audio, anyway.

I didn't know what an ASMR video is so I looked online and it appears to be a "soothing one".

Does this mean there is no speech involved, just the ambient sounds?

If this is the case the simplest, cheapest and best solution would be to record the ambient sounds on your phone, placed well away from the camera/slider and import it into FCP as Luis advised.