I need a help with a product

Hi, I am the inventor of https://www.Ibrush365.com I need an engineer who can help me redesign the product. It is a unique electronic toothbrush , it was engineered in China but it is not working correctly, I got about 40 percent returned due to malfunction, most of the malfunctioning caused by water goes in side the electronic section, I don’t know what else, there may be more problems, an engineer who understand this product may correct all the problems, it may need a redesign, can someone help me please, product is on the market at my internet shop but I am not selling it because I don’t advertise it, I don’t want to have a bad news before even I started, thank you Alexander Kandemir