Hi Lena
Sorry for your issues.
What software are you using? Premiere, Avid or ?
I see the video is 23.976 and audio 48k. Your sequence settings should be the same as video. Unless it has timecode, the audio has no frame rate. If there’s timecode audio needs to be the exact same framerate as video.
Not 24, but 23.976 aka 23.98. There’s a .1% speed difference between that and 24fps. So audio will drift 6 seconds per hour.
You should be able to sync using Merge clips feature in Premiere.
I had a very similar project that took awhile to sync due to lack of slates, scratch audio, etc. Some cameras don’t have audio as they have to buy a separate piece of hardware. Camera guys sometimes figure not their job and won’t pay for the gear. However if they have audio it is unprofessional not to record scratch tracks, especially if they can’t be bothered to slate or even clap their hands.
There are YouTube videos and Adobe tutorials on this. Here’s one
https://www.evercast.us/blog/syncing-audio-in-premiere