It may be moot because multiple things have been tried with varying, mostly no results or progress. May quite likely have made it all worse and unrecoverable.
You may need, for example, to undo everything that has been tried. Disconnect the connection (USB, LAN, wireless) and uninstall any apps or utilities that were installed. Go back the notebook's respective configuration settings. Clean slate - start over while keeping notes on what you do.
There is a learning curve involved with such things and it is not uncommon for any set of instructions (internet or otherwise) to make assumptions that the follower knows to do "X". Without and even with close attention what appear to be the "first best ones" actually are not. Details matter.
What is the immediate priority: getting files on one notebook over to the other notebook? I expect so and the other objective is to be able to rapidly transfer files - correct?
After reading back, I recommend a clean start.
Instead of USB use an ad hoc network. Wired or wireless.
For wired:
https://www.geeksforgeeks.org/how-to-connect-two-computers-with-an-ethernet-cable/
For wireless:
https://www.lifewire.com/what-is-an-ad-hoc-wireless-network-2377409
https://support.structure.io/article/139-how-to-create-an-ad-hoc-connection-with-windows
Whatever method you chose first read through the instructions and preview all windows, tabs, and configuration settings beforehand. Make note of original/default values and what changes (if any) may need to be made.
Plan it all out, step by step.
If something is not clear, then look for similar links that may answer your question(s) or fill in details for you.
Lastly: ensure that you do have backups of the files to be transferred. The backups should be stored elsewhere and off of the two notebooks being connected. Ensure that the backups are indeed recoverable and readable.
Regular backups are a must in any situation or environment.