Hi! 
Products with ingredients like Vitamin A and Niacinamide are really helpful for lightening dark spots. But Vitamin A (retinol, retin-A, retinoic acid) is typically really strong and can cause irritation to sensitive skin. But I've been using a Niacinamide product and it's really helped with evening out my complexion. 

Remember to wear sunscreen too! The sun's UV rays will cause damage to your skin. I was actually gonna write about the best sunscreens to use..soon. Your skin produces melanin to protect itself from external factors like the sun, and that's why hyperpigmentation occurs.
Here's some other products that will help with dark spots! Good luck, and have patience

Dark spots acne scars are indeed difficult to be eliminated. Need time to eliminate it. In addition to performing the treatment on the outside, we also need to consume foods that contain vitamin E, such as tomato, papaya, avocado, banana, kiwi, mango, Psidium, apricots, asparagus, spinach, broccoli, and peppers.

If you are using a particular product does not fit, try switching to other products, it might just fit. Good luck ...