Yes, sitting for prolonged periods of time will negate the benefits of mobs, exercise you do.
Break up your unnecessary sitting when possible. For example, every 30:00 takes a 2:00 break. Get up walk around the office or work place. Quick check in with a co-worker, deliver a message in person etc.

Begin transitioning to a stand up desk if possible. This allows non exercise movement throughout the day. This helps improve focus, productivity, and counter act the negative effects of sitting.

Create strategies for prioritizing mechanics when standing and sitting.
Understanding how to organize& stabilize your body in a good position is key.