BJT to aid switching a MOSFET
Here is one workaround:

Connect the gate of the MOSFET to the collector of Q1.
Connect Q1 to the 10V via a 1kOhm resistor.
Connect emitter of Q1 to ground
This way, the transistor can turn ON completely when driven by arduino.

When the transistor is OFF (base voltage is zero), the MOSFET will be ON (the gate is connected to 10 V via the 1 kOhm resistor.
When the transistor is ON (base voltage above 0,7 V), the MOSFET will be OFF as the gate shorts to ground.
Notice the inversion?
If you do not want the inversion, you have to repeat the transistor logic again (adding Q2), so that voltage at Node A will be in sync with Gate control voltage.


Note: Arduino is assumed to be the Voltage source V2. I have intentionally given a tiny offset to the V2 supply so that one can see both on the graph clearly. ( i am not aware on how to create two different axis in circuit lab).

In your circuit, the transistor acts as a voltage follower. whatever is fed to the input will be presented at the output (Emitter pin). as you know, VBE of about 0.7 V is necessary for the transistor to turn ON. when you feed 5 V, the VBE is higher than 0.7 V and the transistor turns ON. as the current flow trhough the 100 ohm resistor, the voltage will develop. as th voltage starts to rise above 4.3V, the VBE drops below 0.7 V causing the transistor to turn off. Since, the transistor is now turning off, the current starts to reduce through the resistor. The voltage across the resistor drops. This provides a VBE higher than 0.7 V again and hence the transistor turns on again. This process repeats as long as the base voltage is kept higher than 0.7 V and hence the output also follows the base voltage (minus the diode drop - VBE drop).