I don't know where to go.

[Ataeghane]

What is this sentence in Na'vi?

I don't know where to go.
Ke omum oel tsenget a oe kivä tsane. (?)
Ke smon oer tseng a oe kivä tsane. (?)

Do you have any suggestions? Any other ways of saying it?

And what about this two:

I don't know how to cook a worm.

I don't know what to do.

[eejmensenikbenhet]

Oel ke omum fyape/peyfa 'em ngawngit.

This is what I would say, don't know whether it's right or wrong.

[Plumps]

I don't know where to go.
Ke omum oel tsenget a oe kivä tsane. (?)
Ke smon oer tseng a oe kivä tsane. (?)

The first one, I think.

I don't know how to cook a worm.

I don't know what to do.

I circumscribe it via fya'o and fì'u.
Ke omum oel fya'ot a 'em ngawngit

Ke omum oel futa a kem si.

Other suggestions are welcome. There is this, still strange example from Karyu Pawl's blog with fyape that he hasn't come around to explain fully, yet.

[Ataeghane]

Ke omum oel fya'ot a 'em ngawngit

Shouldn't we use 'ivem? I see this like that:

Ke omum oel fya'ot a 'em ngawngit.
I don't know how I cook worm.

Ke omum oel fya'ot a 'ivem ngawngit.
I don't know how to cook worm.

Ke omum oel futa a kem si.

Again, it looks like I don't know that I do, not: I don't know what to do. Is, then, oel ke omum kemit a sivi correct?
BTW, is futa a correct?

[Plumps]

[...]

Ke omum oel futa a kem si.

Again, it looks like I don't know that I do, not: I don't know what to do. Is, then, oel ke omum kemit a sivi correct?
BTW, is futa a correct?

Don't know about the first one...

*kemit a sivi doesn't seem right to me. There was only one instance where si could be placed on its own.

No to *futa a futa = fì'u-t-a so you would have a double relative pronoun

You could go for another construction altogether. How about "Concerning the cooking of worms, I can't to it." Tì'emìri ayngawngä oe ke tsun tsakem sivi.

[`Eylan Ayfalulukanä]

What is this sentence in Na'vi?

I don't know where to go.
Ke omum oel tsenget a oe kivä tsane. (?)
Ke smon oer tseng a oe kivä tsane. (?)

Do you have any suggestions? Any other ways of saying it?

How about simply:

Ke omum oel futa pesenge  oe kivä

[omängum fra'uti]

[...]

Ke omum oel futa a kem si.

Again, it looks like I don't know that I do, not: I don't know what to do. Is, then, oel ke omum kemit a sivi correct?
BTW, is futa a correct?

Don't know about the first one...

*kemit a sivi doesn't seem right to me. There was only one instance where si could be placed on its own.

No to *futa a futa = fì'u-t-a so you would have a double relative pronoun

You could go for another construction altogether. How about "Concerning the cooking of worms, I can't to it." Tì'emìri ayngawngä oe ke tsun tsakem sivi.

Si can be placed on it's own any time the context makes it clear what the missing word would be.  I think that kem a si constructions would qualify there.

Oel omum kemit a sivi
I know what I would do

[Ataeghane]

How about simply:

Ke omum oel futa pesenge  oe kivä

Even if, you should insert ne in there. But still, ke omum oel tsenget a oe kivä tsane seems to me to be more logical than ke omum oel futa pesengene oe kivä.

Oel omum kemit a sivi
I know what I would do

Look like I know what to do and I like it.