sleeping ((Sleeping- should 有大"s")

1. How many hours do you sleep everyday? Why?
It depends, on weekdays, ((delete this , (comma). In English we call this mistake a comma splice. Commas are used to give the reader a chance to "breath' Try reading the sentence outloud, do you pause to take a breath when you read "It depends, on weekends,I sleep at least 7 hours...etc)) I sleep at least 7 hours to guarantee I have enough to wake emerge ((emerge is an odd word choice here. Emerge is used when you are rising, so for example "I emerged from the water"))  the next day. while at on weekends, I could can sleep as much as possible.in fact , I really love sleeping.
2. Is it necessary to sleep enough?
Definitely yes, if I lack of sleeping, I would be exhausted in the next day. sufficient ((make sure you a big letter when starting a new sentence （大 letter)) sleep could give us a nice day.
3. Is taking a snap ((do you mean nap?))  important?
Definitely yes, If((since you are not starting a new sentence, "if" is not captalized (if does not have a big letter))  I have not taken a snap ((when you say "nap" it means you are sleeping during noon))  on the noon, I would be shattered((exhausted) in the rest of my day.
4. Do old people sleep a lot?
As far as I know, fewer seniors sleep a lot, just like my gamy, she is nearly 90 years old, she only takes sleeps barely 5 or 6 hours a day, so I don’t think so. ((you need to write what you don't think: "so I don't think seniors sleep alot")) 
5. Do you think staying up late in is a good thing?
Undoubtedly no. (("Undoubtly no" is not a sentence. In English we call this mistake a sentence fragment. A sentence needs to have a person, like you, I, or me.  If you wrote: "I doubt staying up late is a good thing" then you sentence would make more sense ^^.))   It is really bad for your health. And you will look shattered ((shattered means broken to pieces. When someone lacks sleep does their body fall to pieces? I think exhausted is a better word choice here)) the next day ;moreover, you would like to do nothing but sleep.((excellent transition!))

I think your English is progressing nicely; however, you like to use odd words in context. I think you could fix your odd word problem by consulting (or viewing) a dictionary. 

你說英文太好了！我幫你英文。你幫我的中文碼？