Flag file 'afterfirstboot.lock' not found, can't complete install

Openhabian looks to be installed. As mentioned, you need to cd then sudo. The cd means to change directories and the sudo is for root privileges. You place everything one one line just leave out the $.
When you see the $ symbol everything on the left of it tells where you are. e.g. /etc/openhab2/items$ this tell’s me I’m in the items directory and items is in openhab2 directory and openhab2 is in etc directory. If you need to go back one directory type cd space then two periods or cd space then two minus signs to go back to your home directory.
To fix the FireMotD problem type cd /opt/FireMotD hit enter and notice you are now in the /opt/FireMotD$ directory. From here you can type sudo ./FireMotD -l -v to fix your issue.