Adverb
Verb (する)
Onomatopoeic
1. diligently; seriously; earnestly; reliably; steadily; legitimately
2. perfectly; properly; exactly; orderly; punctually; regularly; safely; in good condition
言うべき言葉も、ちゃんと決めたから多分、大丈夫。I've properly decided what I should say, so it's probably fine.
3. sufficiently; satisfactorily
4. quickly