You don't have to give me 2000 yen. It's only 500.
You gave me too much money. It's only 500 yen, not 2000.
ーYou don't have to give me 2000 yen. It's only 500.
「2,000円も払う必要はないですよ。500円ですから。」
You don't have to give me ...yen. It's only ....を使って表現できます。
ーYou gave me too much money. It's only 500 yen, not 2000.
「頂きすぎです。500円で2,000円ではないので。」
You gave me too much money. で「お金を払いすぎ」=「もらいすぎ」と言えます。
ご参考まで!
You really don't need to pay ¥2,000, ¥500 is more than enough!
・You really don't need to pay ¥2,000, ¥500 is more than enough!
You really don't need to pay 〜(〜も払う必要はないですよ)と ¥500 is more than enough(500円で充分すぎるくらいです)を繋ぐことで伝わります。
・I can't possibly take ¥2,000 from you, ¥500 is plenty!
「あなたから2000円もいただくわけにはいきません、500円で十分ですよ!」という意味の表現です。