I can confirm it works after changing but I needed to have this in my
terminal:

httrack <http://www.something.com/> --mirror --max-rate=999999999 -O
/home/myaccount/downloads/httrack/

The max-rate says about "bytes/second", so 999999999 bytes is 976562 kilobytes
and it is about 953 megabytes, of course one "9" can be thrown away, but I
need up to 20MB/s. So to not calculate exactly what I need I trusted 9999....
pattern : )

Maybe there is no such visible change in the terminal but I am checking size
of the destination folder and it's growing in "bytes" quickly now.