* I don't know it well: This is the most literal translation and is suitable when talking about a specific object or concept.
* I'm not very familiar with it: This is a slightly more natural sounding translation that emphasizes a lack of knowledge or experience.
* I'm not very good at it: This translation is used when referring to a skill or ability.
* I'm not well-versed in it: This is a more formal translation that emphasizes a lack of depth of knowledge.
Ultimately, the best translation depends on the specific context and the nuance you want to convey.