Student or Learner
which one is correct ? i am going to buy this one or this one i am going to buy.
"I am going to buy this one" is more natural.
You should get used to capitalize I (1st person singular pronoun) every time you use it, as well as any word starting a sentence.
Please note that you must not leave a space between words and question (or exclamation) marks. Besides, it is a good idea to include the sentences in question between inverted commas (or any other way that clearly marks their beginning or end) to make them clearer for the reader.