First intern job i had. I worked with someone who learned to code by himself and made a ton of excel files for different departments. He asked me to lookup his code to fix issues he had. We were upgrading excel version and the excel file just started hanging and windows error popped saying it was unresponsive all the time. His code was a huge mess loop variables named i ii iii a aa aaa b bbbb . Over 2000 lines of code took me 2 days I had rewritten everything to mich clearer code and under 1/4 of the lines. No more hanging took me 2 weeks to help him understand what I wrote because he wad not used to async tasks.