Solder the battery connections to the lipo charger board (RESPECT THE CORRECT battery POLARITY!)

Solder the motor to the hacked circuit board across the capacitor (polarity irrelevant, since motor rotating direction irrelevant because shaver only oscillates)

Check the functionality by charging the battery (ONLY red light when charging and ONLY green light when fully charged - both lights indicates incorrect wiring) and turning the shaver on to rotate the motor (it rotates very quickly and silently)