What computer operating system is involved? Are you working from 12 or the 12.1 Update which is obtained using an opened project's Help Menu/Updates?
Please describe you computer resources - processor, clock speed, installed available RAM, free hard drive space? Is your computer optimized?
What are the properties of this 2 hour long video? What is its source?
How are you trying to import this video into the project - Add Media/then what?
Is your only problem this video with its format and duration?
Let us start here and then decide what next.