Q.hibiscus yellowing leaves?
Do I need to water more or less or what do you suggest?
The soil should be moist, but never soggy. When the top inch or so of soil dries out, then watering again--throughly.
Make sure you water so the entire root ball is watered and excess water drains from the container.
On warm dry days, you may need to water twice a day.
Yellowing leaves can be caused by a few other things, so the article below will help you.