I have made some relations, some queries, calculations, filters and so on on my first report. Then I saved that and saved a copy for a new kind of report and then some more reports. When i have to add data, make more relations and so on I have to do it manually in all report. That seems like a stupid workflow. How can I do it better and more efficient?
You can consider using combination of power bi template files and parameters. With parameters you can use multiple copies of power bi template files and then for each copies of reports change data source. This will help you in managing multiple copies of reports by taking away step of configuring data sources for each but you will still require to manage relations.