How can I see my whatsapp notifications on my lock screen?
You can use the DashClock Widget and the DashClock WhatsApp Extension from Google Play and place the widget on your lock screen.

DashClock Widget: https://play.google.com/store/apps/details?id=net.nurik.roman.dashclock

WhatsApp Extension: https://play.google.com/store/apps/details?id=com.stallware.dashclock.whatsapp