To check all the other details of the device use, this link : Huawei P20 lite
Google Assistant Setup
Note: You can also be asked to activate the Voice assistant where you will be asked to record "Ok Google" three times.
You can also watch this video for detailed information about Google Assistant
You can check the complete specs of this phone: Huawei P20 Lite
5G is a cellular technology regulated by the 3GPP organization. Technology and its parameters or bands have yet not been finalized and nothing can be said of now.
You can see full specs here: Huawei P20 Lite
Visit the Play store and search for WhatsApp Messenger. One you find it, open it and tap on install. Tap on "Agree" to start the download.
You can check the full specs here: Huawei P20 lite