Okay, a little background information to start: I'm an English-speaker who has been born and raised in the southern United States and has picked up the western accent of my father. It is the only language I know, and I'm often studying more of it to become familiar with how it works.
I had joined a chat group a long while ago that specializes in teaching foreign-learners English, and I had done so in the hopes that I may be able to help others who need it and learn things myself while I'm at it, but as a native speaker, I'm often seen as a reliable person in which whom I can be asked questions to, but that's where a lot of my trouble begins.
Anything that can be considered a correct-the-mistake question is easy for me; They present to me a sentence that's grammatically incorrect, and I correct it for them, but I'm often asked WHY it has to be constructed the way I've corrected it, but I'm not able to give them a proper explanation, especially with the advanced topics. If I try, I'm often not giving the correct information or have forgotten exceptions.
It can get to the point where the validity of my native speaker title comes into question, and it just confuses me as to how I am able to correct these mistakes without knowing the proper reasons as to why they're like this. Does it have something to do with picking up the language during childhood? Do any other English-speakers have this issue? And if I'm not properly educated about syntax and grammar, where can I go in order to better understand how my language works and functions?