polish something up
phrasal verb with polish verb [ T ] uk/ˈpɒl.ɪʃ/ us/ˈpɑː.lɪʃ/
(OBJECT)
擦亮，磨光（尤指金属或木制品）
to rub or brush an object to make it shine, especially a metal or wooden object
Robert was polishing up some old silver candlesticks. 罗伯特在擦拭一些旧的银质烛台。
(SKILL)
改进，提高（尤指长期荒废的技能）
to improve a skill, especially when you have allowed it to become less good over a period of time
I really must polish up my Japanese before we visit Japan next year. 明年我们去日本前，我真得恶补一下我的日语。