Have a problem growing basil indoors, the leaves are small and cur

May not be sufficient lighting,over or under watering,insects. https://www.gardeningknowhow.com/edible/herbs/basil/information-on-how-to-grow-basil-indoors.htm

Basil likes to be in well-drained, nutrient-rich soil. It also requires 6 hours of sunlight daily. You can amend your soil or make sure you've got a nice potting soil mix by repotting it in the same pot but remove some of the soil. You can then check if it's got soggy feet. If you can't put it by a sunny window for its light requirements, try a plant growth light. The LED ones are a little more initially, but don't spike your electric bill.

Because growing indoors is far different than outside, even if in the same pot. Could also be the variety of basil too.