As far as I can tell the "very good" example is stronger than the "pretty good" one. Like pretty good is actually somewhat good and very good is just awesomely good :) I hope this helps. Anyway don't take my word on this I'm not a native English speaker

Thank you for your explanation. I was able to understand the content very well.

Very good" means something is really, really good. It is "good" to a high degree ("very" is used as an intensifier). "Pretty good" and "fairly good" are the same. They both mean something is moderately "good" (the "goodness" is average).