Which is one correct?
I didn't study grammar as much as i did in the first year
I didn't study grammar as much as i had (studied) in the first year

I'm a bit confused, the first sentence sounds natural, but it seems like both actions occured in the same period of time, and they didn't. ''I didn't study grammar'' happened ''this year'' but it's past, and ''in the first year'' happened before ''this year'', so it's past in the past. To me both sentences seem correct, maybe the first one is acceptable in colloquial speech, but from a strict grammatical point of view it's incorrect? I'm really unsure. Is there anyone competent enough to explain this?

Question

Which is one correct?
I didn't study grammar as much as i did in the first year
I didn't study grammar as much as i had (studied) in the first year

I'm a bit confused, the first sentence sounds natural, but it seems like both actions occured in the same period of time, and they didn't. ''I didn't study grammar'' happened ''this year'' but it's past, and ''in the first year'' happened before ''this year'', so it's past in the past. To me both sentences seem correct, maybe the first one is acceptable in colloquial speech, but from a strict grammatical point of view it's incorrect? I'm really unsure. Is there anyone competent enough to explain this?

Answer

The first is certainly correct. It's also natural. 
You say "so it's past in the past", but that doesn't make sense in English grammar. Past is past. There is no 'more past'. 
The time period for 'I didn't' would need to have been stated or implied previous to this sentence, otherwise we don't know when it is referring to. But that's the same for the second example as well.
There is no need for the continuous nature of the past perfect tense, and no reference to the time period that it covers, so it is not appropriate to use it here.

Answer

1. Earlier past events or situations are indicated by the past perfect tense. 
2. The past simple tense and the past perfect tense are often used in the same sentence.
e.g.: Several senior employees had left the company by the time the new manager arrived.
earlier past >>              senior employees had left.
more recent past >>	new manager arrived.
so i think the second sentence is the better grammatically but in colloquial speech may be yo can use anyone of them .

Answer

Which one is correct?********

لا تفوّت فرصة تعلّم لغة جديدة وأنت مرتاح في منزلك. تصفّح مجموعتنا المختارة من مدرّسي اللغات ذوي الخبرة وسجّل في درسك الأول الآن!