I started last week. or I have started last week.
I preparing for the exam now.
I started last week. or I have started last week.
Why we can meet the first option if the tense last from then to now?

Question

Answer

Correct statements

-1- I am preparing for the exam.  I started last week.

-2- I have been preparing for the exam since last week.

More information:
https://www.ef.com/ca/english-resources/english-grammar/present-perfect-vs-simple-past/

Answer

Thanks for your comment!

Answer

Hey,
The first sentence is wrong, you have to write i'm preparing instead of i pre.. because you are using the verb present continous.
For your Qst, I started last week is the correct one.