When copying from Win10 64Bit to Android smartphone (Samsung) only empty folders?

Hi everyone! I have the following problem. I've never experienced this before. When copying some folders from my laptop to my smartphone, only empty folders are copied. During the respective copy processes, I don't even get a copy progress indication on the screen. It copies the folders and subfolders, but all the files are omitted….

Why is copying a 225 GB MP4 file so much slower than copying a 40 GB file?

Okay, sounds like an unnecessary and very simple question, but the matter is actually a bit complex: I wanted to copy a 225GB MP4 file from an HDD to a brand new SSD, both drives are NOT the system drive C. At first everything ran normally with 80MB/s but then it went downhill rapidly. Then…