Which sentence is correct?
let's start where we left off
let's start from where we left off
let's start off where we left off

Question

Answer

The second one is correct.

Answer

In spoken English, especially casual spoken English, both the first and second sentences are fine.  While technically, the second sentence is better, both are understanable and frequently used.

The last sentence would be understood, but it is awkward and I have never heard someone say it or write it.  The first "off" in your sentence makes it awkward.

Evden çıkmadan dil öğrenme fırsatını kaçırmayın. Deneyimli dil eğitmenlerimizden oluşan seçkimize göz atın ve ilk dersinize şimdi kaydolun!