Por favor muéstrame oraciones como ejemplos con "formal grammar" and "formal expressions" in conversation. . Dime tantas expresiones diarias como sea posible.

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In English, talking formally is more about being polite. for example instead of saying,
"Come over here John" you can say
"John, could you please come here?".

Try not to be too direct or sound too confident. You can use words like
"Pardon" or "Excuse me?" Instead of "What did you say" or "What?" If you want to ask for permission you can use "May I..."
"May I look at those documents?" Even though these are polite ways of saying things, it still sounds stiff. I wouldn't worry about it that much, but it also depends on what workplace you are gonna work at. If the work is like construction (for example), you don't really need to be that formal but if it's business you probably do.