Hello,
1) Here is video tutorial how to update theme:
https://www.youtube.com/watch?v=KdWESIIPU1k
The video tutorial is for Legenda theme, but the process is identical.
2) You can install Coming Soon page in Theme Options->Import/Export.
Also you can find some plugins here:
https://wordpress.org/plugins/wp-maintenance-mode/
Regards,
Robert Hall.