RPi4 as NAS - Transfer Speeds?

This is my first time setting up a Raspberry Pi4 (8GB). Before, I have used a RPi 3B for some other things. From what i have read is, that IO performance should be a lot better on the RPi4, as with the RPi3B. But i get the same speeds as before. I have setup the following:

• Installed Raspbian Lite (64bit)
• enabled SFTP/SSH
• Setup a user for SFTP only access, with home on a connected USB HDD
• the USB HDD is connected to one of the USB3 ports
• This is the same setup on the RPi3B

When I now try to start to copy a 2GB file from my Laptop via LAN, i get in both cases a max of 11.6 or 11,5MB/s. But according to articles like this (https://www.jeffgeerling.com/blog/2021/raspberry-pi-25-gbps-16-tb-omv-nas-setup-and-performance), it should be much faster. Is there some secret, or whats the problem?

BTW: The Laptop runs on Manjaro Linux, where i start the transfer, there is no Windows available.