1.4 grammar question about desu

みはさん こんにちは,
I’ve being studying the dialog of lesson 1.4. It starts with:
あなた   は  にほんご   が   はなせます   か？
So far, so good. The topic is you, the subject is the Japanese language that is being asked if the topic can speak.
The answer is:
はい、 げも  すこし  げか  がけ。
I can’t get the desu. This is working as the copula ( = ) but what is equal to sukoshi deka? The fact that I can speak Japanese?
Would the more complete version be:
(あなた  は  にほんご  が  はなせます) すこし  がけ  げす。

Could someone lay some light on this desu?

Thank you
 

The hiragana is wrong in the answer and so is the answer in romaji.

The hiragana should be:
あなたは　日本語が話せますか。Excuse the kanji I prefer to use it.

はい、でも　少しだけです
はい、でも　すこしだけです。

hai demo sukoshi dake desu
yes but little only do

desu is a casual form of de gozaimasu or de arimasu. Some Japanese people will make it even more shorter and casual if they try to speak really fast.

It is basically saying "it is" or "exists" or "are" there is no direct English translation for many words in Japanese and picking up on their grammar will take time.

If you think of it in English it is like the
Q Do you speak English
A "Yes just a little" (with desu equivalent) or "Yes just little"

Hi Tony, thank you for your reply.

I could get the meaning of the sentence but I’m trying to get the grammar here.

In the audio lesson Kenny said that desu was performing the copula function, so it is saying that something is “equal” to another (if my understanding of the copula is correct). One of the things is “just a little” (sukoshi dake), my question is, what is the other thing that should be equal to that. Or maybe my understanding of the copula is not correct.

Thank you again.

I do not use words like that "copula" and find it over complicates things.

Desu should be considered equal to "It is" 

寒いです
さむいです
samui desu = cold it is
English = It is cold. Without desu you are just saying cold.

今日は月曜日です
きょうはげつようびです
kyou ha getsu youbi desu = today monday it is
English = Today is Monday.

I totally agree with Tony.  Maybe Kenny refers to it as a copula because it glues the sentence together. If you think of it as a conjugation of "be" you´ll be fine.