Losing 15 years of important files is a major setback.
There are data recovery software programs available that can attempt to recover overwritten files from your laptop's hard drive.Important to note: Stop using your laptop immediately to increase the chances of recovery. The more you use the laptop, the higher the chance of permanently losing the overwritten data.
Access OneDrive online through a web browser and go to the Recycle Bin section. You might find your files there.