Slow download with my server

I have nextcloud in docker container, version 14.0.3
OS: OMV4 on debian 9
when I use FTP, then the speed is 7-8 MB/s, when using a nextcloud - 1-2 MB/s, what am I doing wrong?
they are installed on the same server
Update. I use external storage and connect locale directory, I think it’s solve my problem with slow download speed