When bargaining in English, it's important to be polite but firm. Here are some useful phrases to help you negotiate prices:

Start with a statement about your knowledge of the item's value:

"Hey, don't try to rip me off. I know what this is worth."

Ask for a discount or a better price:

"Can you give me a little deal on this？"

"How about giving me a discount？"

"Is there any discount on bulk purchases？"

"Can you make an offer？ Give me a discount."

Inquire about the lowest price you're willing to accept:

"What's the lowest you're willing to go？"

"Is that your best price？"

Express your willingness to walk away if the price is too high:

"If the price is higher than that, we'd rather call the whole deal off."

Show satisfaction with a lower offer:

"It's a bargain."

Remember to keep a friendly and respectful tone throughout the negotiation to increase your chances of reaching a mutually agreeable price.