Well in other languages it is on the desktop version, maybe they will add it later.

Same

If you look closely, ichi is a few pixel longer. Yay, Japanese!

I've never see the long vowel dash except with katakana, so I think it's hard to misunderstand...

The dash is used to extend the vowel sound in a katakana word. You will only see it used with katakana, so as long as you can read the word itself, there should never be any ambiguity as to whether it is a long vowel or the kanji for one.

let's take a break. you may enjoy "いっぽんでもにんじん” on YouTube. it is a video clip for children to remember 1 to ten.

You usually use the context to differentiate between the two. Reading ahead just a little bit helps as well, so if you see a つ right after the 一, like in this sentence, then it's probably the character for いち, rather than the vowel dash.

There might be another way, but I'm not sure of it.

一つ is read ひとつ in this context. I think (but am not sure) that つ is a counter particle for the group of objects that table is in. Alone, Duo translates it as "one" or "one piece."

In this case, "one" is "hitotsu". I've heard it used before, but I'm not sure if it's just "one" or the subtlety is "the only one", as in "This table is the only one there is."

please check out this one: http://www.guidetojapanese.org/learn/complete/counting

I don't know why you got a downvote. This is a good explanation, and please let me make it more clear: There are two counting systems in Japanese, and are not interchangeable.

Chinese system (On'yomi) is used:
1. For numbers + 時 or 月 to mean "o'clock" or "month", except 四時-よじ.
2. For the dates of a month, or when counting days over 10. Notice that 十九日 is じゅうくにち. 2. With most counters, like 羽 (わ, for birds), 冊 (さつ, for books), etc, except 4 and 7, for which Kin'yomi is still used.
3. With 百 (ひゃく, hundred), 千 (せん, thousand).
4. When just counting 1, 2, 3 or read a string of numbers.
There might be some consonant mutation, and you have to memorize them.

Japanese system (Kun'yomi) is used:
1. For the general counter つ (See tips notes).
2. For the dates of a month from 1st to 10th, or when counting days, from 2 days to 10 days.
3. For counting people, 1 and 2 (See tips notes).

There might be some missing or wrong parts, please correct me if I made a mistake. In my opinion this is the most difficult part to memorize in basic Japanese, but it's easy to tackle: Just read them every day until you get used to them.

Tables indeed did not exist in Japan. Japanese style table - ちゃぶ台（だい） is a lower version of table used on tatami. See https://ja.m.wikipedia.org/wiki/ちゃぶ台

It forces you to learn by mistakes which increases the learning efficiency. I found this in all the other courses that I have taken too.

The "tsu" at the end of 一つ is the counter. It's the general counter meaning roughly "X number of things."

you can use either.

テーブルが一つ (ひとつ) あります。

Or in romaji: "*teeburu ga hitotsu arimasu"

Sorry for the late response. Your posts are showing up for me (on the desktop version), and I got an email notification for both of your comments.

I was having the same problem as you a few weeks ago on my Android device. Some people's profile pictures and display names also refused to load for me. I sent in a feedback form, but at the time of writing (8/11/2017) the issue hasn't been fixed yet.

It is pronounced ga hitotsu, and that's what I hear on my audio. You may be mis-hearing the ga and hi sounds blending together.

Here, I think of が as the "subject particle". It indicates that テーブル is the thing doing the verb, あります "to exist". More specifically, it is "one thing existing" (一つあります), so "there is one table."

You just did. :-)

Should be correct

Ko is for small things.

Yes it means there is/are and literally, "(subject) exists." Anything special you want to be explained?

Because the Japanese sentence doesn't specify a location and Duo wants you to learn ここ = "here".

This sentence could be used in response to the question "What is in your spare room (which we are not currently in)?" and thus, "There is one table here" is incorrect.

I would say it should be acceptable, though I think "a single table" subtly emphasizes the oneness of the table more than the Japanese sentence does, much in the way "only one table" would.

If you use が, it is a plain sentence "there is a table"

If you use は, "As for the table, there is one."

あります means "exist as an inanimate being," whereas います means "exist as an animate being." So in normal usage, put あります if the subject is not an animal or human, and います if it is.

There are special usages of these though. Just for some advanced reading so skip it if it does not interest you.

• ～[noun]であります - this is the long form of ～です (The ending stuff you have to put after a noun to end a sentence.) - This actually means "exists as" So 私（わたし）は　学生（がくせい）です means that "I exist as a student" i.e. "I am a student." It is taking the subject as a concept so always inanimate.
• ～[verb]ています - this います adds the meaning to the verb so as to represent a continuous action or state of the verb. ごはんを　食（た）べて　います - I am eating my meal. 映画（えいが）が　はじまって　います - The movie has started (treat it as "continuously in the started state"). I think it is always います because it emphasize the "continuation" of the verb which is something like "animation."
• ～[action verb]てあります - This means an action (verb) has been performed and the state after the action remains. It emphasize that someone has prepared the state by doing the action. - ドアを　開（あ）けて　あります - The door is kept opened. 手紙（てがみ）を　書（か）いて　あります - The letter is written. It describes the state after the action so always "inanimate."