Pages templates contain placeholder text, entered to show what a block of text will look like on the page, without the distraction of holding any specific meaning. The language of that text (Latin) is immaterial, as it is intended to be replaced with whatever words you want to put on the page, and you'll place these words in whatever language you choose.
Click on a block of text in the templets. Start typing.
Or click on the text, go Edit > Paste and Match Style to replace it with text you have copied from elsewhere.
What exactly do you expect will happen?
That despite typing English, text inexplicably will be changed into the strange language?
That there are mysterious instructions as to what to do hidden in the foreign language?
Just click in it and see what happens when you add your own text. Exploration leads to discovery.