While there is no global setting that would allow you to change the report's language, you can do so manually. If you want to use this report multiple times for different clients, you only have to do it once, because the report can be saved as a team template, or you can create widget templates.
Widget Title and Description
Click on a widget and select the "Titles" section on the right side menu. Any text that you type will be saved automatically.
Metric and Dimension name
When hovering over the metric or dimension, click on the 3 dots and select "Rename metric/dimension". Type the text that you would like to see and click on "Rename" to save your changes.
You can also rename the metrics on a graph/chart/list/goal widgets in the following way:
