Is it possible to make a Nav Mesh agent only walk straight paths and stop a certain amount of time every time he changes rotation to walk into a different direction?
You can get the points where the NavmeshAgent will turn either directly with NavMeshAgent.steeringTarget or first getting the NavMeshAgent.path and then the corners. Then you should monitor the movement of the agent (probably in a coroutine), set the angularSpeed to 0, and whenever it gets close to a corner set the velocity to 0 as well until the waiting time passes. Then you first allow it to turn by setting a higher angular speed, and when that is done, you allow the velocity again. Repeat until target is reached or path becomes invalid.
I hope this helps, please respond with your solution if you succeed with it!