Why slow data transfer speed through SMB android 4 and windows 10?

Question

Android

There is a beelink x2 media player with android and root.
I use the SambaDroid application.
A flash drive (FAT32) is connected to the player.
When copying one file from Windows 10 to the player's flash drive, the copy speed does not exceed 1 Mb/s.
If I copy two files, the speed drops to ~100 Kb/s
Why is that? How to speed up copying?
I would like the copying speed to be at least 20Mb / s - is it possible?
I also installed an FTP server on the player, through FTP the speed is kept within 2.5Mb / s