To say "了解一下" in English, you can say "to know" or "to understand" or "to learn about".

The origin of these words comes from Old English. "To know" comes from the Old English word "cnawan", which means "to know, to recognize, or to perceive". "To understand" comes from the Old English word "understandan", which means "to comprehend or to grasp the meaning of something". "To learn about" comes from the Old English word "læran", which means "to teach or to instruct".

Here are some examples of these phrases in English with Chinese translations:

"I want to know more about your project." (我想了解一下你的项目。)

"Can you help me understand the rules?" (能不能帮我了解一下规则？)

"I'm interested in learning about your culture." (我对了解一下你的文化很感兴趣。)