Thumbs up [Q] My Phone is getting slower

Hey Guys hope you all are fine
Today i have a question that "my phone is getting slower" i have s2 hd lte korean (shv-e120l) it have 1.5 ghz dual core processor and 1 gb ram the amount of free ram is 270 to 300 mb but i don't know why my divice lagging

Give me the solution please..or some mod links that makes my divice usable