Certified GKH Gardening Expert
If this is a tropical hibiscus, then it may be severely damaged, but may come back. If it is hardy, then losing leaves will not harm them. They will come back, naturally.
You may cut back the dead growth of the branches when you start to see new growth again.
Here is an article that may help: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-plant-varieties.htm