I have ardunio uno because i can easily upload code but now it shows error stk 500 not responding

Using Arduino Avrdude, stk500, Bootloader issues
2

What is the project that you were working on when it started to fail?

Just some points:

  1. Which operating system are you using?
  2. Did you select the correct port?
  3. What is the serial-to-usb converter on your board?
    An official Uno will have a 16U2, clones might have a CH340 or other chip.
    If your board does not use the CH340, have you done the loopback test? What are / were the results?
  4. Is the board properly detected by the operating system?
  5. Anything connected to pins 0 and 1? Remove it and try again. If that fails, remove anything connected to the board (except PC) and try again.