Re: google now not working
Follow the instructions on Google's support page to enable Google Now: https://support.google.com/websearch.../2824784?hl=en
Since updating to 4.4.3, you might also want to consider clearing the device cache by going into recovery. For the Nexus 5, power off the phone, hold volume up+volume down+power. When the start screen displays use power down to select Recovery then power to accept. On the next screen (android with exclamation mark) hold power then press volume up and let go. Use volume down to select Cache and power to accept.
More information to do this in Recovery is available here: https://support.google.com/nexus/answer/4596836?hl=en
Note: Don't select factory reset as that will clear the device.