1 I have long been learning English.
This means you have been learning English for a long time. I would also say that is a rarely used construction (to have long been doing sth) - it's not wrong at all, but we would probably be more likely to say "I've been learning English for a long time".
2 I continue learning English.
This simply means that you are learning English now and that you started learning in the past, but it gives no hint as to when you started. It could have just been last month!
Could you tell me what the difference, if any, between them is? Thanks.