To doing something with someone.

[JockZon]

How do you express that you want to do something with someone. In the company of someone else? How do you say 'I want to talk japanese with a japanese.'

Watashi wa nihonjin to nihongo wo katatai? (My japanese stinks )

[metablue]

Ooh, is it "ni wa"? A fairly random guess. I'm trying to figure out how to use it.

Watashi wa nihonjin ni wa nihongo wo katatai?

[JockZon]

I have learned in class that the particle to means with but maybe you should not use it in this case, I really do not know.

[Brody]

A simple way would be to say 日本人と日本語を話したい（です。）

(You're right: と basically means "with.")

You can leave out わたしは if you want. ～たい is only used for first and second person, that is, you only say ～たい to mean "I want (to do)." To ask if you want (to do), you would turn it into a question, thus people would be able to know you weren't saying what you wanted to do (This of course doesn't take into consideration a question such as "I want to speak Japanese with a Japanese person?" or a statement like "You want to speak Japanese with a Japanese person." But don't worry about those; they would only be understandable from context anyway)

For a third person (i.e. "He wants to speak Japanese with a Japanese person") you use, ～たがる。　So, （彼は）日本人と日本語を話したがります。

Here's how to conjugate for ～たい/～たがる：

Class 1 Verbs (i.e.　行く、話す）　Change the last hiragana to its い equivalent in the hiragana chart. So, 行くー＞行き、　話すー＞話し and add たい。

Class 2 Verbs (i.e. 食べる、見る） Drop the る and add たい.
So, 食べるー＞食べたい、　見るー＞見たい。

Class 3: するー＞したい、　来るー＞来たい

Same for ～たがる. Just add たがる instead of たい。
するー＞したがる
来るー＞来たがる

Hope this helps.

[JockZon]

More than I really wanted to know but it was really helpful. I know you could drop the watashi but I wanted to be sertan and I also know how to express that you want to do something but you went into it deeper so I understand it more.

Arigatou

[usagi]

Hi JockZon-san,

The way I learnt it was also to use the "to". So, I would agree with the version posted by Brody-san.
Here´s how it was explained to me:
For your own hopes and wishes you use the stem + tai/desu.
(Explained really well above!)
Just one point to add: if you use a verb which takes the particle "wo" you can use either "wo" or "ga" when followed by the tai/desu.
e.g. eiga wo mitaidesu
or eiga ga mitaidesu. (I want to see a film).

And for doing this with someone it becomes: nihongo no tomodachi to eiga wo mitaidesu.
All other particles stay the same e.g. itsuka eiga ni ikitaidesu. (I want to see a film someday).

For someone else´s wishes you could use quotations : ....to itteimashta (so-and-so said...) or the aforementioned "tagatteiru".
My sensei translated this as "I think that he/she wants to because of the way he/she is behaving" !!!
If you use this remember the particle "wo" stays the same and doesn´t change to "ga" this time.

Have fun learning.
Take care

[Bueller_007]

For someone else´s wishes you could use quotations : ....to itteimashta (so-and-so said...) or the aforementioned "tagatteiru".
My sensei translated this as "I think that he/she wants to because of the way he/she is behaving" !!!

Have fun learning.
Take care

Yes. What many teachers don't tell you at first is that がる is used to change adjectives into verbs. (In this case, たい into たがる.) がる means "to show signs of feeling a certain way".

So for example:
〜が欲しい (to want something) -> 〜を欲しがる ([to show signs of] wanting something)
〜が怖い (is scared of) -> 〜を怖がる ([shows signs of] being scared of)

That's why it's more natural to say:
彼はその犬を怖がっている。

Unless you're a mind-reader.