Here are some routes that you might consider.
Exit Neumünster-Mitte (14), follow the B430, in Hohenwestedt change to the B77 in the direction of Itzehoe to the destination.
Exit Bad Bramstedt (17), follow the B206. Drive through Hohenlockstedt on the B77 towards Hohenwestedt to your destination.
Exit Itzehoe Süd (10), follow the B77 to the Aral petrol station, turn left onto the B206 to the Esso petrol station, then take the B77 towards Hohenwestedt again to your destination.
Exit Itzehoe Nord (8), left twice, straight ahead over the roundabout towards Schenefeld, right to Hohenaspe, follow the road to the B77. B77 towards Hohenwestedt to the destination.
From Bad Segeberg on the A21, exit Wahlstedt (11) on the B205 to A7, then continue as “Coming from A7 from Flensburg”.