Zuòshì bùyào tōutōumōmō de, guāngmíng-zhèngdà yīdiǎn.
Don't be so sneaky about things, be more open and upfront.
Tips
grammar
偷偷摸摸 follows the AABB reduplication pattern common in Chinese adjectives/adverbs. It can be used as an adjective (偷偷摸摸的行为, sneaky behavior) or adverb (偷偷摸摸地走, to walk sneakily).
usage
偷偷摸摸 always carries a negative connotation, implying dishonesty or guilt. The shorter form 偷偷地 is more neutral and just means 'secretly.'
