There can be a lot of factors that can help with improving the CTR, i.e. images, pricing, reviews/rating, and value for money, you need to figure out what is that’s holding you back, and you need to improve on that thing, which will ultimately improve your CTR, so let’s suppose, your images are great, but your pricing isn’t just cutting it, you need to either bring it down to provide more value for money or be more competitive with it.
