Well is an adverb and good an adjective that must be followed with a noun :)

You can be good at something or you can do something well. I am good at speaking English. I can speak English well. You cannot exchange well and good in these sentences. We are 'good at' activities. We 'do' activities 'well'.

well = adverb good = adjective of course = sure = certainly

Helena just remember : this food tastes .. good ...but also "he is good at making nuisances" she does her job ...well (because it's an activity ) but there are some exceptions, such as " well done" because it's undertood that there was an action. generally speaking when there is an activity ..it's well * are you sure of what you are saying? of course I am sure ( obviously you are sure)

of course and sure can be used to express the same or different thoughts depending on context. i.e. "Can I borrow your car tomorrow?" Sure or of course would be appropriate responses here as they are both ultimately taking the form of 'yes.' in a different context for example... "Are you sure (to be right, positive, or accurate) you remembered to turn off the oven before leaving the house?" Of course (absolute assurance/agreeing statement) I remembered, although sure I remembered would work as well. i.e. He is very sure (confident) of himself. But you could not say... He is very of course of himself....that wouldn't make sense.