Ještě ne.
Usage and formality
Used to indicate that something has not happened or been done, but is expected to in the future. It's a polite way to decline or postpone.
Watch out
Use this exact phrase for "Not yet." only in a matching register and setting.
Notes
Used to indicate that something has not happened or been done, but is expected to in the future. It's a polite way to decline or postpone.