bike/car turning indicator circuit using 555 timer IC

Hi Arjit, Like my professor always states, "If building circuit is a skill then debugging is an art" Anyone can look at the circuit diagram and make connections to build a circuit. Most times you cannot expect a circuit to work in the first try. You have to perfrom Debugging. You will be able to debug a circuit only if you can understand the working of the circuit.

The circuit you have here https://circuitdigest.com/electronic-circuits/vehicle-turning-signal-circuit is a pretty simple circuit. It has a 555 timer working in astable mode to provide constant pulses these pulses are then used to control leds through 4 NPN tranisstors. Because the current given out by the outptu pin (pin 3) will not be enough power all LEDs. To debug the circuit you first have to make sure your 555 timer is woring properly.  To do that you can try this circuit https://circuitdigest.com/electronic-circuits/555-timer-astable-multivibrator-circuit-diagram first and make a single led blink. Once this is done you can add transistors to blink 4 leds one after the other.