Is it possible to connect multiple GND with one wire?
Depends upon how "zero volts" your grounds must be.

Notice I wrote ground(s)

Make a list of grounds, and write down the trash levels you need.

Then identify the DC currents flowing, and compute the I*R. Compare this to your list.

And identify the power supply trash currents, and compute the 

V = L * dI/dT

using estimated inductance of 1,000 nanoHenries per 1,000 milliMeters.

You can reduce the power supply trash currents, producing very small dI/dT, with small series resistors and large capacitors.

I call these "local batteries" because the DC comes from your power supply,  but the transients now come from the large LOCAL capacitor. 

The series resistor is essential to isolation, and for dampening.

1 ohm and 1,000uf are good values. Notice this is a 160 Hz low pass filter.
Mind the DC drops.

Where you ground the capacitor ----- is critical.

============= edit ============

using a STAR ground will help, if the star is the lowest impedance point --- that means the star must be at the battery, or the gnd output of your power supply

Using MOSFET GATE DRIVERS may help to separate sensitive regions from fast-switching regions; the input will be logic levels; the output can be 5/12/18 volts as needed to control your high current motor-driver FETS. Have 0.1uf right across the gate driver, so the fast gate-charging currents come from that cap. And maybe 1 ohm or 10 ohm in the VDD to the gate-driver, to localize the surges.

Basically you need to make sketches and visualize where the fast current surges flow. Using remote gate-drivers is  one way to move fast edges away from your MCU.