The MIUI, system apps and launcher doesn’t work properly

My phone’s connectivity, system apps, system launcher don’t work properly and lags too much. Earlier it lagged only when the connectivity signal of the SIM card and the calling feature is used but it stopped sim support and WiFi doesn’t work anymore. After factory reset , it is showing setting app being crashing after resetting the phone. The system apps, connectivity doesn’t work anymore System UI doesn’t work well and crashes again and again.