Put files from PC onto a Samsung Galaxy S7 via Wifi?
SSHDroid + WinSCP. I think it doesn't even require root if not using port 22 (you don't have to). Also allows resume transfer. Been using the combination on my own tablet whose USB MTP connection is not working.

Don't expect transmission speed to be high, though - 2MB/s at best and ~200KB/s at worst, far slower than USB.