Djing with playing live keys?

It would depend a bit on which software you'd like to use ... if it's rekordbox, the DDJ-400 is compact, simple and straightforward. If you'd prefer Serato, then the DDJ-SB3 is the equivalent in features and size.

As you're using a MIDI controller keyboard and not one with a built-in audio output, you would also need to consider how the DJ software interacts with your DAW or production software, and how the audio would be routed and output.

Thank you for your reply!!
I was thinking to buy the ddj sx2 whats your opinion and which would you choose?

It's certainly a lot larger, but if that's got the features you want and isn't too big, then it's a great controller - I've been using one for years. But again, you'd still need to consider the audio routing for the production side of things.

You are asking a classical pianist everything for me is new now 😁
So let's say I buy the ddj sb3, in the case I want to sing live too
Which other device I need to buy?
Yes I'm a singer also :)
Good thing is sb3 is much lighter and cheaper yea 😆

Okay, so let's as the big question -- how do you do it now? What software do you use with your keyboard? Do you already have an audio interface? Do you have a mixer to which you connect a mic?

I learned how to dj in the cdjs350..with the mixer250, playing only with usbs
Now I want to advance my skills and combine what I know to do. So piano djing and singing 😅
My midi is playing with the ableton which I don't really like so far, but I'm willing buy and do everything most practical and easy to shake my dream true.
I gonna follow your advices step by step 🙏