Ask at the forum if you have an Ancient or Modern Greek query!
P. and V. βεβαίως, V. ἐμπέδως.
firmly: P. and V. βεβαίως, ἀσφαλῶς, V. ἐμπέδως, ἀραρότως (also Plato but rare P.).
faithfully: P. πιστῶς.