The phrase "sleek over" is not commonly used in English, but you might be thinking of the phrase "gloss over." "Gloss over" means to cover up or minimize the seriousness of something, such as a mistake, fault, or a problem. When someone glosses over something, they try to make it seem less important or serious than it really is.
Whitewash: This idiom means to cover up wrongdoing or to make something appear better than it actually is.
Smooth over: This phrasal verb means to make a problem or disagreement seem less serious.
To "gloss over" something is to avoid talking about it in detail, often in an attempt to minimize its importance or seriousness.