Okay thanks 
sudo apt list --upgradeable
says
python3-acme/xenial 0.31.0-2+ubuntu16.04.6+certbot+2 all [upgradable from: 0.25.1-1+ubuntu16.04.1+certbot+1]
anything else that should be ugraded?
How can I confirm that ACMEv2 is in play?
kind regards Hubertus