Hi Alexandr,
That’s a good start 
What do you see in GitHub for your PR ? Do you see Checks of SonarCloud in the tab “Checks” ?
Note that PR decoration now happen in Checks on GitHub and there are no more comments in the Conversation tab.
Are you using the Travis-CI addon to set up your analysis? It’s pretty straightforward, you can have a look at our example : GitHub - SonarSource/sq-com_example_java-maven-travis: Java Maven-based project analyzed on SonarCloud using Travis
Hope that helps