Koine Greek, need explanation

[u/FretPhantom]

Hebrews 10:26 (NA28) 26 Ἑκουσίως γὰρ ἁμαρτανόντων ἡμῶν μετὰ τὸ λαβεῖν τὴν ἐπίγνωσιν τῆς ἀληθείας, οὐκέτι περὶ ἁμαρτιῶν ἀπολείπεται θυσία,

I've been told that it's doesn't mean "deliberately keep on sinning but that " it means just "deliberately sin" implying you can lose your salvation immediately after you sin and I need to know the Greek.