Stonger motor for Arduino Robot?

I need to improve the speed of my Arduino Robot for a competition but I don't know which stronger motor I can use. I don't want to ruin my robot so please help me.

Any feedback is very much appreciated.

Motor selection is based on a Design Criteria, which, not surprisingly , you have not provided:

DESIGN CRITERIA
1- PHISICAL SIZE (CAN DIAM, LENGTH)
2- RATED CURRENT : Max Current, Peak Current
3- Rated Voltage : Max Operating Voltage
4- Torque ? (optional)
5-Inductance ? (optional)
6- RPM: MAX RPM @ MAX VOLTAGE & CURRENT

Any feedback is very much appreciated.

How? You provide no numbers at all… Rather than play the guessing game,
please post all the relevant details (more is better - photos, datasheets, requirments…)