Will it help improve my credit score if I keep a credit card with good credit limit but usually don't use it?

Well, this is not gonna improve your credit score. You need to charge your credit cards even if it is for a small amount. But make sure, you are paying off your outstanding balance amounts in full on time. Hopefully, you can see an improvement in your credit score after a certain time.

Yes, I agree with Craigh.terry. However, keeping that credit card means having a higher credit limit. So, it helps in a low credit utilization ratio which is a contributing factor of a good credit score.
But I always tell not to keep lots of credit cards which becomes difficult to manage properly.

Well, this is one of the factors. But you have to repay the full payment within the time. Also, manage other monthly payments to see the difference.

Use it to make small purchases and pay the balance in full every month. It will help to improve your credit score. The festive season will start soon. If you have to make any large purchases, then you can use this card without increasing your credit-utilization ratio too much. This can help you to avoid a credit score drop.