De or het projectplanning?

The correct Dutch article is:

de projectplanning

Rule Words ending in -ing: almost always de. See the rule

How to use projectplanning

the projectplanningde projectplanning
this projectplanningdeze projectplanning
that projectplanningdie projectplanning
our projectplanningonze projectplanning
your projectplanningjouw projectplanning
every projectplanningelke projectplanning
which projectplanning?welke projectplanning?
a big projectplanning / the big projectplanningeen grote projectplanning, de grote projectplanning