How long to learn Japanese?

I know nothing of Japanese or Chinese language. How many take long I can learn one of these two languages?
Which one is easier and more regular?

Of course I think priority is with Chinese language because in addition to the great trade exchange that is between China and Iran, many Chinese travel to Iran or many Iranian travel to the country, so I can work as a translator in such the wide dealing and traveling. What is your advice?

A lot of which language to learn and how long it takes to learn it depends a lot on your personal motivations for learning the language. As well as how motivated you are. Learning any language fluently takes years of learning. As to which is easier or more beneficial once again depends on your motivation and learning habits.
If your preference leans toward Chinese it will likely be easier for you to learn as you're more inclined to want to learn it. That's my personal opinion on the matter.

Mansoor,

I would say a couple of years. Of course, it will go faster if you live in that country.

For me, Japanese is a lot easier than Chinese, although I know of people who say Chinese is easier than Japanese.

If you want to learn Japanese, the first thing to do is learn hiragana. If you want to learn Chinese, the first thing to do is learn pinyin (with all of its 'exceptions').

がんばって！ (Gambatte!) 加油！ (Jiāyóu!) Good luck and try hard!

It is about five years that I am practicing English and still have a lot of errors, but what I have to do with a language with 700 alphabet!!
So based on your guidance, it will be very hard that I can learn Japanese or Chinese language in a short or even average period of time.

It's an entirely different language with it's own rules, words and sentence structures. Unfortunately there's no easy or quick way to learn all of that. It's a lot of information. The best way of course is immersion but your ability to do that will of course depend on your ability to relocate to a location where they solely speak that language, failing that speaking regularly with a native speaker of the language.

As you've already done quite a bit of work learning English I would expect it would take just as long to become as fluent in another language. If your motivation to learn that language is as much as your motivation to learn English was.

Short answer is, there's no easy or short way to become fluent in another language. A lot of books will get you conversational in a short period of time, but the majority of the learning is a slow and difficult process. The best way to start out is to try to find some material in your native language.

I lived in Japan for two years and worked hard to learn the language. While in the Navy there , I took a college course on Japanese with two big text books and audio tapes. I lived off base with Japanese friends and used Japanese every day. At the end of the two years , I would say my Japanese was only equal to a 6 or 7 year old child. I found Kanji almost impossible to learn. I also spent some time learning Russian , German , French and Spanish , and by far , found Japanese the most difficult to learn.

One of the most difficult things in Japanese or Chinese language is the shape of their alphabets and words. They has their own shape and standards that are not recognizable for somebody who wants to learn the languages. The alphabets have a shape similar to things and objects. A series of vertical, horizontal and lopsided short lines that each one has a particular angle to the adjacent or crossed line. learning and memorizing such the alphabets seems to be very hard, especially that I have heard the number of the alphabets are about 700!

Of course such the languages should have a grammar book ten times thicker than oxford!
Although I am interested to learn Chinese or Japanese but apparently learning such the complicated alphabet and grammar rules seems to be very laborious and take a long time.

I am happy to meet you again, uncle sam LoL... ( just a joking with you)

Yes, actually learning Japanese and Chinese languages is very hard, though I have not stepped into the class yet.

Although, I am very interested to learn one of these two languages, but my problem is that I am not patient enough to spend a long time for such purpose. In fact, I am not a good studious person to be able to memorize complicated things. I mostly love to learn things transiently and fast, out of academy, this is because I have not learned English completely yet, after six years!

I am approximately an intelligent person, but my failure is that I don't like to spend a lot of my time for memorization, this is because I didn't go to university earlier. I mostly like free studying to understand things, but the fault of this manner is that I don't memorize names, numbers and details as they should be memorized. Of course it is not a good manner and is unlike the manner of the wiser persons who use their complete memory and attention to memorize everything in detail , but I mostly follow my interest in such type of studying, instead following the fundamental manner of educating.
You told, you examined learning some other languages in addition to the Japanese. Why you didn't try to learn Chinese either?

Mansoor,

The most important thing in learning Chinese is that you love the Chinese language. If you do not love it, do not try to learn the Chinese language.

As someone who's studied several languages to varying levels of proficiency, I'd say Japanese is very hard. I find collocation of vocabulary difficult, and the way they often use different words, grammar and syntax than English to explain a particular idea is difficult to get the hang of, without reverting to a literal translation of what you would say in English, which often sounds weird and unnatural in Japanese.

As with any language or skill, you need to be practising pretty much daily (reading, listening, speaking) if you want to get proficient at it, and for quite some time.

There is not difference between Japanese and Chinese for me. Both peoples are good, kind and intelligent.
In the competition of technology both countries went advance with a wonderful rate, though Japan was pioneer.

In recent years, the condition changed and China outrun Japan in the voluminous industrial production and subsequently outdoor trade. That was because China decided to modify its economic affairs comprehensively and goes out from the foreign trade depression.

Japan didn't drop behind in technology, but it had a notable failure in progression of economic policies, and it was because of its fault in an comprehensive international economic activities, so today China is in a high position economically!

This excellent condition help it to be able to do more comprehensive research and innovation in technology and also increasing the quality and quantity of its industrial productions which raise its rank more and more in the global economy, so far as, it can compete with America and Europe.

This great progression and economic progression had a notable effect on fame of the Chinese language, and nowadays, many people in the world try to learn Chinese due to the purposes such as mutual economical dealing and marketing and also great mutual traveling and transportation.

The priority of Chinese language to Japanese is because of this issue.

I like both the Japanese and Chinese, but the second says to me, if you are seeking for a prosperous job and good income, please learn me!
Nonetheless, I think learning each one of these two difficult languages is very hard for me.