Indeed, I should test it with more than one connection.
I found that results vary...Even when doing the same tests, with the samen configuration, with the same file, the speed is never exactly the same!

The machine I was running it on was a my second pc for years.
It contained a celeron 333 that was a gift together with a newer motherboard.(I used it for my study)
It had been running red hat 6 & 7 & 8 for years, using the celeron at a higher clock speed. (as smb server)
Original when posting:
333(66)
Overclocked (config before sme server)
500(100)
Because of the RAID 1, and the new disks, I was thinking not to risk the disks or processor getting hot.
When the processor runs at the higher clock speed, I get at least 8.6 MB, and uploading starts at higher speeds.....
I tested this at least 5 times now

and ever time the processor runs at a higher bus speed, the increase happens...
I am going to look for a faster processor. I never thought that a celeron was not fast enough for a one user fileserver, and would slow down ethernet..