It's "最近（さいきん-Sai kin-）" But when you say "I'm studying japanese these days" we often say "今は日本語を勉強してます。（ima wa nihongo wo benkyou shite masu）" 今は-ima- means "now" or "currently" Also you can say 最近日本語の勉強を始めました（saikin nihongo no benkyou wo hajime mashita） It means "I started to learn Japanese recently." Hope it helps!

You would say "I've been studying Japanese lately." in Japanese, too. I'm a native Japanese speaker, and I would say so personally. "Saikin Nihongo o(wo) benkyou *shite imasu." (*"shite imasu" is more formal than "shite masu." In conversation, "shite masu" is more often heard.) If you say, "ima wa", then the particle "wa" emphasizes the temporariness of the action. (You've been doing it for now, but you may stop at any time.) You could say, "ima nihongo o(wo) benkyou shite imasu" to say your current situation.