First of all, I have to say that this sentence is grammatically incorrect in English. The correct forms would be: "It would have been better if I had completed my studies." or "It would be better if I had completed my studies."
The former is the common third conditional form and the latter is the mixed conditional. Both could be used because one may imply that the situation would have been better in the past if the other action had happened, which is the first sentence, or one could convey that the situation is always good/better in general which is the second sentence.
In both cases, Persian speakers use more or less the same structure being: "بهتر بود اگر درسهایم/تحصیلاتم را تمام کرده بودم" or "اگر درسهایم/تحصیلاتم را تمام کرده بودم بهتر می شد"
I'll also be glad to show you how you can express yourself well in spoken Persian.