I would do them in this order:
ci(github): add basic build pipeline for android and backendci(test): run automated tests in github actionsci(github): optimize workflow with gradle cachingci(sonar): connect repository to sonarcloudci(sonar): add sonarcloud analysis to github actionsci(quality): configure initial sonarcloud quality gatesci(quality): require passing quality checks before mergedocs(ci): document pipeline sonarcloud and quality gate workflowcigithubsonarqualitydocstask