How will it affect my credit if I return my ...

I would do a couple of things. If your credit is so bad return the car and let them take it.

If you have decent credit ask the bank if you can refinance the note lower interest or even an increased payment period.A bank does not want your car and will work with you. 

I need an answer for this question also ,,,what can I do if I can not pay the loan for my car b/c,,yes i am up to my payments but struggling to pay month by month also de insurance is to high. I will like to know if I can bring my car back to the dealer or I need to pay a penalty?

it will show on your credit as a voluntary repo which does hurt your credit the car will be sold at aution and you will owe the balance in which it doesnt bring from the payoff plus a repo fee  hope this helps