No problem with your english, much better than my Indonesian (even if my wife is half Indonesian 😀 ).
It’s a good question and here in the West it really is a no-brainer. Gear is easily available and at very reasonable prices. To not have a controller is really not necessary for most.
Our founding father, Phil Morse, started his digital DJ-ing career on a Sony laptop with DJ software using only keyboard shortcuts. He played big events in public that way. So, yes, it can certainly be done that way.
With that said, I think Phil will be the first to agree that having a controller makes things a LOT easier. So if you can afford one, having a controller is definitely gonna help you with your practicing. It can also be used for those small (house or pool) parties where no gear is available. And even going to venues where they do have CDJ players, you will easier switch from being used to a controller to them, than from switching from keyboard only.
Hope that answers your question a bit.
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