The depedent form of feic and talking about things you've witnessed or heard in Irish.
Is this sentence correct?

Ní fhaca mé néal sa spéir. = I didn't see a cloud in the sky.

Also, how does one talk about more complex things they have witnessed or that they did not witness? For instance, how do you say:

1. I didn't see him hit the girl.
2. I saw him cross the street.
3. I watched the ducks swim across the lake to the other side.

Also with the verb clois:

1. I didn't hear him yell at the girl.
2. I heard him walk upstairs.
3. I heard the ducks swimming across the lake to the other side.

Question

The depedent form of feic and talking about things you've witnessed or heard in Irish.
Is this sentence correct?

Ní fhaca mé néal sa spéir. = I didn't see a cloud in the sky.

Also, how does one talk about more complex things they have witnessed or that they did not witness? For instance, how do you say:

1. I didn't see him hit the girl.
2. I saw him cross the street.
3. I watched the ducks swim across the lake to the other side.

Also with the verb clois:

1. I didn't hear him yell at the girl.
2. I heard him walk upstairs.
3. I heard the ducks swimming across the lake to the other side.

Answer

"Ní fhaca mé néal sa spéir" is correct.

You can express more complex ideas in embedded clauses like this:
1. Ní fhaca mé ag bualadh an ghirseach é.
2. Chonaic mé ag trasnú na sráide é.
3. D'fhéach mé ar na lachain ag snámh an locha trasna/anonn (dóibh).

In some cases you can also break up the sentence by making a subordinate clause:
2. Chonaic mé é agus é ag trasnú na sráide.
3. D'fhéach mé ar na lachain agus iad ag snámh an locha trasna/anonn.

Similarly with "clois":
1. Níor chuala mé ag tabhairt íde béil don ghirseach é.
2. Chuala mé ag dul suas an staighre é./Chuala mé é agus é ag dul suas an staighre.
3. Chuala mé na lachain ag snámh an locha anonn/agus iad ag snámh an locha anonn.