Especially in the light of Zuckerberg's recent behaviour, please consider using Signal, it's actually good and a pretty easy replacement for Whatsapp

https://signal.org

Signal Messenger: Speak Freely

Say "hello" to a different messaging experience. An unexpected focus on privacy, combined with all of the features you expect.

Signal Messenger
@joelanman @wolfgangcramer
also a good option is using #Threema as a WhatsApp replacement, yet it is not free of charge. In my opinion 5€ for a Messenger app fulfilling the german DSGVO act is fair. (server Software is not open source...)
A messenger comparison is available here: https://www.messenger-matrix.de/
(Credits to @kuketzblog)
Messenger-Matrix • Kuketz IT-Security Blog

Messenger: Vergleich sicherheits- und datenschutzrelevanter Eigenschaften von Messengern