Can you provide a link to this DJ device? It would also be nice to know what ‘chinch cables’ are, as I don’t recognize the term. 

Important to remember that all analog line ins on Sonos have the 75ms delay, while digital line ins are shorter. For DJ work, Sonos has proven over and over to be unsuitable, in many, many threads of people trying. It has also, in these many threads, been suggested as an ill advised hook up. 

You would need to use:
 

RCA analog out of the DJ console to an analog-to-optical converter.

Optical out of the converter to the optical in on the Sonos optical-to-HDMI-ARC adapter.  

HDMI-ARC out of the adapter to the HDMI in on the Arc.

But why would you want to?  You would need to disconnect the Arc from the TV every time you wish to DJ, and any grouped rooms would be delayed from the Arc, causing an echo.  As stated by ​@Airgetlam, Sonos (or any wireless audio streamer) is not compatible with live performance due to the buffering which takes place in order to ensure reliable, stutter free streaming. 

In fact I need to connect DJ console, only for one party, it’ll not be a permanent solution.

Then my suggestion will work.  Just know that only the Arc and any Sub/surrounds will be in sync.  Any grouped rooms/speakers will noticeably echo.

Not chinch, but cinch. See https://blog.teufelaudio.com/what-goes-where-audio-cables-explained/#:~:text=Cinch%3A%20Cinch%20or%20RCA%20plugs,left%20channel%20white%20or%20black.

Thanks, I’d only heard them referred to as RCA cables. Much like TOSLink cables, I assume from the manufacturer who came up with the originals. 
 

Edited: Huh, it’s even stated here: 

https://en.wikipedia.org/wiki/RCA_connector#:~:text=The%20RCA%20connector%20is%20a,the%20design%20in%20the%201930s.

Thank you very much for your help!

To sum up, DJ’s consol with Arc + Sub will work correct, but in the multiroom system I’ll recognize delay ~75 ms?

Converter like below should work?

(sorry I didn't find it on the English page)

It’s looks fine 2xRCA on the Input side, and optical at the output side:

KONWERTER CINCH 2xRCA NA TOSLINK SPDIF PRZEJŚCIÓWKA AUX ANALOG -> CYFROWY - Sklep, Opinie, Cena w Allegro

Yes, that will work.  You will also need the optical-to-HDMI adapter that came with the Arc.