How long had you been learning English?¿

How long have you been studying English? or How much time have you spent learning English? or How long did you study English.?

Your example: "How long have you learned English?" My suggestion: "How long have you been learning English?" This means you are currently learning, and you simply give the amount of time you've been studying. Answer: "I have been learning for five years [so far]." Your example: "How long did you learn English?" My suggestion: "How long did it take you to learn English?" This means that your study-period is basically over, you're proficient enough with English to have stopped studying and the question is about how long the process took from start to finish. Answer: "It took me ten years [to obtain a level of fluency]."

Hello M Shaf! I liked your comment! Thank you so much for your explanation! Your answer the best!