muck about

/M AH1 K AH0 B AW0 T/
verb
  1. 1

    To do random unplanned work or spend time idly

    โ€œStop mucking about and get on with your work!โ€

  2. 2

    To attempt to do something with a piece of equipment without understanding how it works.

    โ€œDon't muck about with the video machine, or you might break it.โ€

  3. 3

    To be playful; full of fun and high spirits; to not treat the situation seriously.

    โ€œIt was only a joke. We were only mucking about.โ€

Source: https://en.wiktionary.org/wiki/muck%20about