From any section of the app. Find the Themes available located at the top right corner of the screen and click on it.

Then select the theme you would prefer, let's pick the dark for example:
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Now that you've selected a new color theme it will show as you selected.
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From any section of the app. Find the Languages available located at the top right corner of the screen and click on it.
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Then select the language you would prefer, let's switch it to spanish for example:
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Now that you've selected a different language texts will show in the language you selected.

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