Efficient means doing things in a right way while effective means doing the right things.
Example:
Situtation:
You are an employee given the task to shop for the supplies needed at work.
Effective → You buy the things you need and also did some window shopping sincw you're already there. Yes, you achieved your goal but you wasted time
Efficient → you buy the things you need and went straightly back to your office. You wasted nothing :)
Thank you! Hope this'll help you :)