Step 1: Go to make.powerapps.com
Step 2: Go to Setting. Look for the ⚙ icon in the top right corner.
Step 3: A dialog pops up and with language settings.
Step 4: you can change the language you want from the drop down list under Choose language.
Step 5: Choose a language and click Save.
Step 6: Refresh your browser and see that the language is changed.
Hope it was useful.