Are these sentences/translations correct?? WA-GA-NO-WO practice. (japanese-english)

Nihongo wo hanasemasu ka. - can you speak japanese?
Hai, hanashimasu. - yes i can.

Nihongo ga hanasemashu ka. - is it japanese that you speak?
Iie, eigo wo hanashimasu. - no, thats english.

Dare no hon desu ka. - to who belongs this book ?
Watashi no desu. - it belongs to me.

Dare ga isha desu ka. - Who is the doctor?
Rikusan ga isya desu. - Riku is the doctor.

Sushi wo tabemasu ka. - You eat Sushi?
Iie, sashimi wo tabemasen. - No, i eat Sashimi. 

Nani wo tabemasu ka. - What is this that you eat?
Sushi wo tabemasu. - It is Sushi.

Dare no tokei desu ka. - to who belongs this watch?
Watashi no tokei desu. - Its my watch.

Anata wa nani desu ka. - What are you? (?)
Watashi wa gakusei desu. - I am a student.

Anata wa gakusei desu ka - Are you this student?
Hai, sou desu. - Yes i am. (?)
Hai, sou desu. - Yes, thats right.

Dare ga gakusei desu ka. - Who is the/this student?
Watashi ga gakusei desu. - I am the/this student.

Nani wo shimashita ka. - What have you done?
Terebi wo mimashita. - i´ve watched TV.

Dare no terebi desu ka. - To who belongs thisTV?
Terebi wa dare no desu ka. - To who belongs the TV?

Terebi wa Rikusan no desu - It belongs to Riku.

Are these sentences/translations correct?? WA-GA-NO-WO practice. (japanese-english)

Nihongo wo hanashimasu ka. - can you speak japanese?
Hai, hanashimasu. - yes i can.

Nihongo ga hanasemasu ka. - can you speak JAPANESE?
Iie, eigo ga hanasemasu. - no, I can speak ENGLISH.

Dare no hon desu ka. - to whom does this book belong?
Watashi no desu. - it belongs to me.

Dare ga isha desu ka. - Who is the doctor?
Rikusan ga desu. - Riku is the doctor.     ----Keep in mind that this way of replying is more conversational

Sushi wo tabemasu ka. - You eat Sushi?
Iie, daga sashimi wo tabemasu. - No, but i eat Sashimi.

Nani wo tabemasu ka. - What is this that you eat?
Sushi wo tabemasu. - It is Sushi.       ------ shita   is past tense of suru  

Dare no tokei desu ka. - to who belongs this watch?
Watashi no tokei desu. - Its my watch.

Anata wa dare desu ka. - What are you? (?)  Who are you? 
Watashi wa gakusei desu. - I am a student.

Anata ga gakusei desu ka - Are YOU the student?
Hai, watashi ga gakusei desu. - Yes i am. (?)
Hai, sou desu. - Yes, thats right.

Dare ga gakusei desu ka. - Who is the/this student?
Watashi ga gakusei desu. - I am the/this student.

Nani wo shimashita ka. - What have you done?
Terebi wo mimashita. - i  watched TV.

Dare no terebi desu ka. - To whom does this TV belong? 
Terebi wa dare no desu ka. - To whom does this TV belong?

Terebi wa Rikusan no desu - It belongs to Riku.

Nice job, 

I suggest you learn Hiragana quickly, it will help you with your Japanese studies.