In that project it was about 100 or so errors that were all really easy to fix (no major refactoring required) so I just sat down and went through the list one

In that project it was about 100 or so errors that were all really easy to fix (no major refactoring required) so I just sat down and went through the list one by one until I had 0 errors, 0 warnings. A lot of the errors were just styling. Some were errors where the value could have been null/forgot a try-catch block (although almost never was in practice unless I changed some code elsewhere accidentally), and a few were so major that one of the features that I implemented wasn't working at all but I never realized (mostly because I was one of the few people using the app and never really tested the feature).