Good day!
I can help You with file sharing qualitatively and quickly because I am a certified network engineer (MTCTCE/MTCNA) having over 10 years of experience in configuring, maintaining and troubleshooting of enterprise network devices, VPNs, and firewalls.
Does remote computer has the Internet before established VPN or not?
What type of VPN do You use?
TeamViewer doesn't work without Internet Access.
I know many ways for file sharing (FTP, SCP, SMB, NFS, RDP and other), so You can choose it as You wish.