If I were to make up words, like ciscalciac or circocalice you would know how to pronounce them, even though the letter "c" is sometimes pronounced as a k, and sometimes as an s. You might have some trouble knowing whether the final syllable of the second one is -iss, -ese, or -ice, but you'd get the c's right. There is a rule there and you know it internally, even though you may not know it consciously. Children who are good readers can stumble through words they are less-familiar or even unfamiliar with and get this rule right. Cerulean and cerise, concatenation and concentration, culinary and currency, they can usually get them right after about ten years old.
Originally all the c's were k-sounds. Some of them changed to s-sounds. The key is the following letter. If it is a back vowel, a, o, or u, the c keeps the k-sound. If it is a front vowel, an e or an i, it moved to the s-sound. It happened in French before the Norman invasion, and the words came to us after the 11th C. Italian words like cello mess up this rule, but that ch-sound is part of the same process.
The letter C has an interesting history in itself. Etruscans are involved, turning the Greek gamma, our hard-g, into a k sound, which the Romans then picked up. A kid could get a good research paper out of that which would send their teacher into rapture. But that isn't why I brought this up.
There is an idea in linguistics about internal grammars, that native speakers intuitively know rules they have never even thought to articulate. They know the rule, even though they didn't even know there was a rule. Some things sound right, others don't. The order of adjectives is another set of internal rules we just know. "Metal ancient five spears" just doesn't sound right, though we understand it well enough. We just know, at some level of certainty, that Five Ancient Metal Spears is the correct format. In languages with more declensions and conjugations such as Latin, Greek, or outrageously, Finnish or Inuit*, word order doesn't matter as much. Because English dropped those in the great simplifications as Saxons, Vikings, and Normans overran the territory, we went to word-order instead. People like to introduce subtleties and distinctions into their language when they can, to set themselves off from those Auslanders in the next valley, who just don't get it.
Those rules internally understood by all native speakers are the real rules in any language. Rules that you have to teach children as late as high school are not the real rules of a language, not in Mandarin, not in English. Those non-intuitive rules might be extremely useful to teach children, especially minority children who aren't going to get the benefit of the doubt in conversation. But they are not in any sense "more correct." They are the rules of the prestige dialect of formal discourse, nothing more. What is prestigious in a dialect varies enormously by context. If you speak Episcopalian to Fundamentalists and insist your language is correct you are going to offend.
And vase versa
I have made reference to inequality of intelligence here many times, because it is a neglected topic in the national discourse. Yet we are remarkably equal in intelligence in so many ways, and one of them is language. Native English speakers of many home dialects have remarkable convergence in understanding the real rules of Our Magnificent Bastard Tongue.
You speak English well, whatever your mother-dialect was. There is no logical position that declares otherwise. However, you might have to bend your dialect in the direction of prestige in service to social approval and advancement. If that seems unfair, understand it has been that way in all languages as far as the eye can see.
*That legend of the Eskimos having 200 words for snow? That comes from the many combinations of possible endings in agglutinative languages.