Learning Japanese or any language for that matter takes a very long time…
Lets look at how to say that! —
How long does it take to learn Japanese?
どのぐらい にほんごを まなぶのに じかんがかかりますか？(the direct translation is: how long japanese to learn time is taken? – See what I mean about not bothering to look for direct English to Japanese translations.)
It will take a very long time.
とても ながくかかるでしょう
Is it difficult?
むずかしいですか？
Yes, its very difficult. And it is a lot of work.
はい、 とても むずかしいです。 そして とても たいへんです。