Hello,
We've have just released a new update of the game which should drastically improve the time taken to save your careers (divided by 10 on some laptops).
The updates also contains several bug fixes and optimizations around saving/loading careers.
We are very grateful for the feedback we've received in the last days which has helped us finding the bottlenecks in the saving process.
A new career is not needed to get the faster saving time.
Enjoy the game!