anyone can help with slow HDD speed?

I have Toshiba 1TB, 7200rpm, USB2.0
Inside menu I have apeed sround 140Mbit/s, what should be enogh for HD record + HD Timeshift.
When I recording one chanel (HD or even SD) and meanwhile I'm watching one already stored record, afterward in that currently recorded chanel missing some part.
Looks like HDD is not able to write and read at the same time.

Is the option, how to increase HDD speed?
USB 2.0 should have a limit 480Mbit/s, why I have only 140 in the menu?
Is it better NTFS or FAT32 format?