[Mesorah] Beva'u, Ke'an, Na, Ata

[Aharon Gal]

I am trying to find the meaning of the words ATA and NA in Leshon Kodesh, and Beva’u and Ke’an in Aramaic.
Reading the pesukim seems to me that in most cases ATA is NOW. 
In most cases VE’ATA, is “THEREFORE", or "AS A RESULT”.
In Aramaic I see KE’AN as a translation for NA and also as a translation for ATA
I notices that where NA is after a verb, then the translation is KE’AN.
When it is not after a verb, then the translation is BEVA’U.
BEVAU is also the translation of ANA.

Therefore, can I conclude that NA not after a verb is ANA, “Please”.
After a verb is not clear to me. I cannot say it is “Please” as many time I see that it comes in pesukim that are Hashem’s commands.
My questions are:
1.  what is “NA” in Hebrew when it comes after a verb (in the bible)
2.  What is “ATA”? is it mostly “Now” but sometimes “Therefore”?
3. What is Ke’an” in Aramaic? How do I know when it means “Now”, or “Please” or “Therefore”?

Thanks,

Aharon