Some Huawei phones not provide mobile data when connected to Carsifi WIFI(during Wireless Android Auto session). There are some approaches how to solve it(try each step separatly):
1. Enable "Wi-Fi+" in Settings -> Wi-Fi -> More settings -> Wi-Fi+
2. Make sure Carsifi WIFI is removed from wifi known list. Connect to Carsifi adapter. If your phone asked to connect to WIFI without Internet, ignore this message(don't click on connect or cancel button). This hack helps to make mobile data workable.
3. Add "fake" proxy. Open WIFI settings -> Select Carsifi Wifi -> Edit connection -> Proxy(manual) -> Add fake proxy:
Host: proxy.example.com
Port: 8095 or any.