"fest an etw glauben" in English fest an etw. glauben to be a staunch/devout believer in sth. to have unshakable faith in sth. Detailed translations for "fest an etw glauben" fest an etw. glauben fest an etw. glauben to be a staunch/devout believer in sth. fest an etw. glauben to have unshakable faith in sth.