I first started learning Japanese in high school, when freelance Japanese tutors advertised themselves in my school. I thought that this might be a good opportunity to start learning a language - since back then (and probably still now) there weren't many places you could reliably learn Japanese in my city. This is why I applied to study with them.
I continued to learn the language for 3~4 years and learned up to N3. As far as I remember we used みんなの日本語 (a very popular beginner's textbook) for N5 and N4, then switched to 日本語総まとめ for N3. We also did JLPT N3 tests in order to test my readind and listening comprehension. Unfortunately at some point my family could no longer affort my Japanese classes so I had to drop out. Since then I haven't been learning Japanese actively - I only learn it passively through translation work. A lot of my beginner JP knowledge kind of degraded because of lack of practice, but I also learned a lot of new grammar and vocabulary thanks to reading texts meant for native speakers.
As for which is harder - Japanese is way harder than English. The grammar, for me personally, is okay, but memorizing all the kanji and their readings is hell. Also, I've been learning English since kindergarten so I have a lot of experience both reading and speaking - it comes intuitively to me at this point. The same can't be said about Japanese.
I'd like to once again stress that my Japanese knowledge is amateur and as of now I am not learning it actively (too busy for that). But I can always provide some encouragement to anyone who wants to start out! You don't need a "real" reason to start learning any language, though as a pragmatic person I would suggest you at least consider the benefits of learning it. For example, I would like to learn Spanish in future, and my main motivation is that it's a fairly common foreign language and that I have a Spanish friend.

My recommendations for learning Japanese are as follows:
1. Get yourself an extension/program that lets you look up words. I use Yomichan for Firefox - I hover over a word I don't know and hold Shift, which allows me to see its definition in a dictionary I downloaded.
2. For memorizing words, I would suggest Anki. It can be used to learn any language by the way. It is very easy to use and minimal in its design, which I find to be its biggest strength.
3. You can give textbooks a try. みんなの日本語 and 日本語総まとめ are once I used so they are the only ones I can recommend. Though the latter is made specifically so you can pass the JLPT.
4. Using a dictionary might be nice. I use Takoboto on my phone. Don't really have a dictionary program on desktop but there are plenty dictionaries online, from simple things such as Jisho to something more interesting like A site that lets you look up things in multiple Japanese dictionaries.
5. Read in Japanese to test your skills or practice. I mainly use MINDHACK for this, but I plan to play Marikin Online 4 in the near future. It will probably take me forever to finish but at least it will be good practice.