Thank you for your prompt reaction.
I use iptables to redirect incoming streams on port 80 to another port.
In addition, I deleted all iptables rules, and stopped the application that was running on the redirect port. I then ran the command sudo certbot certonly --standalone -d b2i-dev.tech again with no success.
And yes, I read the answers in English very well. it's the expression and the writing that is problematic for me