Dual displays detected as singular display via usb c dock issue (MBP 2017, Dell)
What you ask is simply not possible with that hardware.

Due to the way the signal must be demultiplexed, you will need a Thunderbolt 3 dock instead of a USB-C dock to be able to drive the two external displays with separate content.

Alternatively you can connect one of the monitors directly to the MacBook Pro using a standard USB-C to DisplayPort cable.