Do you know when to use 'have' instead of 'of'?

If I knew my diarrhoea had the power to explode a toilet, I would of tried my hardest to quell the forces that compel my anus to shoot its wicked cannonballs.
^ do you think "would of" is grammatically incorrect in this example
yepp
nopp
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Do you know when to use 'have' instead of 'of'?
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