So, I watched the log file output.log from NodeBB directory and I noticed two things.
1- The time in log file doesn't respect my system time :
2019-10-18T05:52:57.076Z [4567/1114] - warn: [plugins/load] The following plugins may not be compatible with your version of NodeBB. This may cause unintended behaviour or crashing. In the event of an unresponsive NodeBB caused by this plugin, run `./nodebb reset -p PLUGINNAME` to disable it.
* nodebb-plugin-composer-default
* nodebb-theme-persona
* nodebb-plugin-mentions
* nodebb-rewards-essentials
# date
Fri Oct 18 07:54:00 CEST 2019
2- The server always restart according to log file and sometimes I can see the spin icon on UI.
It is certainly because of the warning precisely telling me that these modules are not yet compatible.
However, I did the default installation without adding a plugin myself.