atefehjan Problem one is a known bug:
https://answers.ea.com/t5/Bug-Reports/NEEDS-SAVES-Can-t-switch-between-Sims/td-p/13907460
If you're willing, please share your save with EA. Instructions are in post 58.
For problem two, are you seeing Error 0? That's also a known bug:
https://answers.ea.com/t5/Bug-Reports/NEEDS-SAVES-PC-MAC-Save-Error-0-Patch-1-86-166/td-p/11414169
That thread is requesting saves as well.
If you're getting a different error when trying to save, please post a screenshot. You can also try using "save as" rather than "save" when you get the error.