Ako gutom na gutom Gutom na gutom ako 

nagtanong ako si sa asawamo ko kung paano sasabihin ng sa Tagalog (I asked my wive how to say "....").
"I will be at home at 5 o'clock in the evening".
Sinabi niya sa akin "uuwi ako sa bahay ng nang sinko alas-singko
oras sa gabi  ng gabi, o - uuwi ako ng nang sinko alas-singko oras sa ng gabi sa bahay".
Sinabi ko sa kanya "salamat po, <em>po and opo indicate politeness yet you are only expected to use it for elders, people of higher social standing, and strangers not with somebody you're on a par with like your spouse and friends </em>ang wikang Tagalog ay mahirap". (I said to her "thanks,Tagalog is dficult!").
Sinabi ng asawamo ko sa akin "Hindi, ang wikang Olandes ang mahirap!" (Sha said to me "No Dutch is dificuld!"
Ako gutom na gutom ako. pupuntahan ako sa tindihan, para bibili bumili ng tinapay at inumin.(I am hungry, I go to the shop to buy bread).

Question: Is Sinabi here the passive (object-focus) of nagsabi and why is it used here?

<em>Because, unlike English, object-focus format is the grammatical default voice of Tagalog. We don't intend to speak passively, it's just that the base form of the clause resembles to English passive voice. Moreover in all Filipino languages, "voice" is often neglected and doesn't affect focus-shift because the "triggers (affixes)"  do the job. My advise, forget about the voice system (active and passive) and master the various "verbal focuses" instead. </em>

<em>Read my post for further understanding:</em>

http://www.italki.com/discussion/71104

Salamat po sa inyong tulong ! 

<em>Walang anuman. Actually you're doing great, keep it up! :)</em>

Nagtanong( tinanong) ako sa asawa ko kung papaano sabihin sa Tagalog ang (I asked my wive how to say "....").
"I will be at home at 5 o'clock in the evening".
Ang sinabi niya sa akin "uuwi ako sa bahay ng alas singko
ng gabi, o - uuwi ako ng singko ng gabi sa bahay".
Sinabi ko sa kanya "salamat po( you're too kind to your wife :) ), ang wikang Tagalog ay mahirap". (I said to her "thanks,Tagalog is dficult!").
Sinabi ng asawa ko sa akin ay "Hindi, ang wikang Olandes ay mahirap!" (Sha said to me "No Dutch is dificuld!"
Ako ay gutom na gutom. pupuntahan ako sa tindahan/ pamilihan, bibili ng tinapay at inumin.(I am hungry, I go to the shop to buy bread).

Question: Is Sinabi here the passive (object-focus) of nagsabi and why is it used here?- Sinabi means s/he said and no its not passive :)

Salamat po sa inyong tulong !

The corrections given by Green are all correct.  Just a few additional points...

- nagtanong ako sa asawa ko kung paano sasabihin sa Tagalog ang "I will be..."

- gutom na gutom ako. pupunta ako sa tindahan, para bumili ng tinapay at inumin. (I am very hungry, I will go to the shop to buy bread and beverage).

You may also replace "inumin" with "maiinom" to mean "something to drink".  

"Gutom ako" = I am hungry; "Gutom na ako" = I am already hungry; "Gutom na gutom ako" = I am very hungry; "Gutom na gutom na ako" = I am already very hungry.  (For all these "gutom" words, accent is on "tom".  "Gutom" (with accent on "gu") = hunger

You may also very often hear "sabi" used in place of "sinabi". -> "Sabi niya sa akin" and "Sabi ko sa kanya"

Evening time here starts at 6:00 p.m.  Hence, "alas-singko ng gabi" should be said as "alas-singko ng hapon", if you were here.  -> "hapon" (accent on "ha') = afternoon; "Hapon" (accent on "pon") = Japanese.