Boing 737 MAX safe to fly again?

Haven't they also fitted multiple stall sensors, so that the computer won't make decisions on the input from only one?
Well, they had multiple stall sensors before (angle-of-attack sensors actually, which can be used as stall sensors.) But the MCAS was only looking at one. Now it looks at both AND it has a warning when they disagree, indicating one is damaged - and when that happens the MCAS does not take input from either one.

Other changes that were not as directly related to the crashes:

Improved wiring to the horizontal stabilizer trim system
Improvements to the software in the flight control computer
More mandatory training for new pilots