I think you got a warning rather then an error.
We will need to refactor the code for PHP 7.2 but I'm sure you can continue to use BreezingForms without any problem.
If you can revert your PHP to 7.0 or lower this warning won't show.
BreezingForms Spanish language:
Backend does not translate correctly into php7.
I have followed your instructions and they do not solve the problem.
Change in my host to version 5.6.30 and without more is already seen correctly in Spanish.