Well, you're a learner so you're probably not going to be attempting to answer other learners' questions most of the time. However, in case you do, I recommend starting with "Not a teacher." (without the quotation marks but with the capital letter and the full stop).
Otherwise, if you're asking a question or making a comment on your own thread, there is no need to preface it with anything. Give us a relevant thread title and go straight in to your question.
The capitalisation rules apply to everyone and everything - capitalise the first word of every sentence, a sentence inside quotation marks, proper nouns and the word "I" at all times. End every sentence with a single, appropriate punctuation mark, whether it's a full stop, question mark or exclamation mark.
Student or Learner