Bard thinks maybe your English is a little lacking too.
"
The grammar of the sentence "I have rarely met an English person that knows 'lose is not loose' nor 'have is not of'" is correct, but it could be improved by making a few changes.
First, the word "that" should be replaced with "who" because it is referring to a person.
Second, the word "nor" should be replaced with "or" because it is connecting two negative statements.
Third, the phrase "have is not of" is a bit awkward and could be replaced with "is not of having."
Finally, the sentence could be made more concise by removing the word "rarely."
Here is the revised sentence: