Short-term, follow the steps on the website and contact your political representative to explain to them why it's such a bad idea.

Long-term, switch to another messenger app that's opensource and truly E2E encrypted.

That also shows why this is such a foolish proposal.

The truly scary people are not on the "consumer" chat apps anyway and most certainly will be the first ones to switch to another communication channel if this passes. If this will have any effect it'll be that some, "dumb" criminals will be caught.