delete – Files and Folders in the WhatsApp folder disappeared automatically

I cannot find my WhatsApp Videos folder.
as you can see here

But the videos are accessible from WhatsApp (not from gallery). Many of the Images have disappeared. I had more than 11k WhatsApp images, but now it shows only 2.4k in the folder. In gallery, the images are unopenable as you can see here

After I restarted the device, the images and the videos came back (as a separate space in the gallery), but in File Manager, I still cannot find them.
see here

What is the probable cause of this? Is my device hacked? And how to fix it?