There are technicians in the maintenance point for more than three years, usually the second-level agent first. Just get a professional qualification certificate. Manufacturers are professional after-sales, and you can't start your own company if you want to do it after-sales. They are on standby at any time. You are always on standby. I just bought an air conditioner online. Other brands don't know. I bought Haier's. Haier was installed by the manufacturer. I bought it in JD.COM.