Native language - Romanian.
1. If you are a not a native English speaker:
a. I started in kindergarten with some very basic stuff, couldn't speak at all but knew some (very very few) words. Then I started learning it a bit more seriously in the second grade (in Romania, that would mean 8 years of age), but I was mostly limited to asking for directions, talking about the weather and various greetings/basic words. Then, the process of learning really kicked off when I turned 10-11, when I started travelling.
I mostly learned it alone, by ear - although I've had private teachers for about half a year, I haven't learned much from them at all. That's the reason why I have for example no problem with English tenses (I think I almost never make mistakes in that regard), but I have no idea how they are called, I just always go with the one that feels right. At 14 I started travelling a lot, and English was my only means of communication. 14-15 was the point when I created a very strong "bond" with English.
Later, the Internet also helped me, especially with ortography and extending my vocabulary. So my timeline would be:
5-8 years old - a few words
8-10 years old - basic sentences and some more words
10-14 years old - started traveling, acquired fluency in both talking and writing
14-16 years old - travelled a lot, acquired almost native-like fluency
16-18 years old (aka 16 - present) - correcting tiny little mistakes that I was somehow unable to see before.
All in all, I would be almost impotent in English if it wasn't for travels. I think I spent about 1/4 of a year abroad, in the period when I was 14-18, and the only language I've spoken was English during that time.
b. what level do you consider yourself?
Native-like. Apart from names of flowers and animals, I believe I have a larger English vocabulary than many English speakers, I don't think I make any grammatical mistakes on a regular basis (everyone makes mistakes once in a while, but simple errors are not the same thing as mistakes due to a lack of knowledge of the language), and I've been told countless times that I have a very well-developed accent. In fact, every native speaker of English I've encountered told me my English sound like a mix of north-American accents. Also, I almost always think partially in English. In fact, I think that I'm probably thinking more often in English than in Romanian now that I'm not in Romania any more.
c. how long did it take you to reach the level you are at? See above.
d. why did you learn English?
At first, because I had to (all kids have to start English in school from grade two - meaning when they are 8 years old), afterwards, because it was the only possibility I had to interact with people when I was abroad. Again, I've mostly learned it alone.
And for the other set of questions:
2. If you are a native English speaker:
a. what other language(s) do you speak?
Romanian (native), German, Italian, and a tiny bit of French.
b. what level do you consider yourself?
Being a native speaker of a Romance language, I can easily understand Italian and Spanish, and I've studied French in school. Forgot almost everything I've learned in French, but I'm still able to entertain a very basic conversation and, when written, I understand it without problems. I became fluent in Italian in about a month, after staying there one summer. Now I lost my fluency, but I can still understand almost everything (it's amazingly easy, after all those years - thank you, Roman Empire!!). I've never had any knowledge of Italian grammar, but it's basically a dumbed down version of the grammar of my native language, which makes it rather easy to guess the right answer most of the times.
At German, it's hard to say. A few months ago, I passed a B2 exam without problems (I was 2 points away from the 100 point maximum, argh!). Meanwhile, I've improved a lot, but I'm not exactly sure where I am right now. I can definitely speak somewhat fluently (hell, I'm working as a teacher, so I must be at least able to "drive" a conversation for hours in a row), however I have serious problems in understanding native speakers talking to each other. If they speak to me, they will usually speak Hochdeutsch (standard German), which is a million times easier than... whatever dialect they normally use.
For example, if my flatmates talk to each other, I'll understand the first 3 minutes and then I'll just kinda phase away, as I'll be missing more and more of the information exchanged in that time. If they talk to me, I have no problem in understanding them. I believe that my grammar is, for my level, basically flawless, but I have serious problems with the vocabulary. I've never had to learn the vocabulary of a language from scratch - there are so many Latin words in English that a good chunk of it was already there, in my mind, since before I started learning it. With German however, this doesn't work as well. Sure, they have many Latin words, but not nearly as many as English does. Hope that by the time I obtain my bachelors (3.5 years from now, spent about 5 months here until now) I'll be fluent in most circumstances, have no problems with slang and expressing my feelings. Right now, I have the feeling that if I speak in German, I can easily convey a piece of information, but I can't really express my feelings - my "flavour words" are missing entirely!
c. how long did it take you to reach the level you are at?
3 months for Italian, 6 years for French (but I really haven't studied it at all, it was just my weekly 50 minutes at school), 9 months for German. Also, since all my colleagues here that study with the same teacher as me are all Spanish and South-American, in the past 5 months I've gone from "understanding some spoken Spanish" to "understanding most of it", unless it's spoken insanely fast, which they tend to do sometimes.
d. why did you learn another language?
French - I had to, in school - any Romanian who finishes high school is supposed to have decent knowledge of one foreign language and at least a basic knowledge of another. For me, French was "the other one".
Italian - I spent 3 months in Italy, I learned what I know without even trying.
German - I'm studying here, and I'm going to remain here at least 3.5 more years (quite possibly more)