1. 你 问了 一个 问题 [ ni3 wen4 le yi1 ge4 wen4 ti2 ]. You have asked a question. 2. 他 刚刚 看了 一部 电影。 [ ta1 gang1gang1 kan4 le yi1 bu4 dian4 ying3] He just now have seen a film. 3. 你吃 饭了吗？ [ ni3 chi1 fan4 le ma1 ] Have you had a meal? :D

As for the beginner level, "le" mainly has two usages. One is "Verb+le" and another one is "sentence+le". According to your description "the particle "le" indicates a completed or finished action", I believe you are talking about the "Verb+le"。 For example: 他打了两次电话。Tā dǎ le liǎng cì diànhuà. He made a phone call twice. 我吃了一片面包。Wǒ chī le yī piàn miànbāo. I ate a piece of bread. 她喝了一杯水。Tā hē le yī bēi shuǐ. She drank a glass of water. Hope this will be helpful~ : )

我做了一个梦。 Wo3 zuo4 le yi2 ge4 meng4. I had a dream (last night). 叶子黄了。 Ye4 zi huang2 le. Leaves have turned yellow.

For example:我吃完饭了。"了“means I have eaten. 我想了想 It means,I thought. "了" sometimes means have done.

你的中文进步了。Your Chinese has improved