"I get together with them."

Translation: Saya berkumpul dengan mereka.

[Son-.-Goku]

I clicked "aku bersama-sama dengan mereka" in the multiple choice and it counted it is correct, but when I click on the discussion tab it shows a different answer.

[MaxPayneBurrito]

Duo is using a database that allows you to use a different answer which would be also correct. The downside is the procedure uses all the options to create choice answers, so you might meet an answer you didn't learn yet.

[kam990]

Why is it bersama-sama?

[MaxPayneBurrito]

Because it's plural. Bersama can be used only in singular, like "kamu" or "dia". If you want to use it for plural, it is necessary to use plural form "bersama-sama" or "berkumpul".

[Kane645532]

what is the sama

[MaxPayneBurrito]

As an adverb, "sama" means "together" or "jointly".
It has variety of meanings in a different part of speech.

[Stewart737090]

What is the difference between berkumpul and bersama?

[TonyBerjaya]

What wrong with "Saya bersama dengan mereka"?

[MaxPayneBurrito]

Bersama can't be used for plural, plural would be "bersama-sama" or "berkumpul"

[Alex489754]

Berkumpul means gathering
Bersama means together
If Iam not wrong they should Chang it