Blank UI

Ok i managed to access the terminal via a remote connection.
And think i managed to do all the instructions except for the last one:

When i try to launch the very last command

“husarion@rosbot-78975:~$ roslaunch rosbot_webui demo.launch”

I get this error message:

[demo.launch] is neither a launch file in package [rosbot_webui] nor is [rosbot_webui] a launch file name

I noticed that demo.launch exists in rosbot.webui/launch

Sorry but my linux abilities are null.