"Aber er erfährt nichts."
Übersetzung:But he does not find out anything.
Its also a bad sign to use the word "ain't" in text form except in either descriptive or artistic use. However starting a sentence with a conjunctive (and, but, though, also) is generally considered bad form. There are some cases where it is allowed, although a sentence beginning with "but" is only allowed in artistic use.