It was most probably a manhwa, less likely a manhua. It started on this situation :
There was an auction , but it was like two people fight in the ring ( probably boxing) and the loser would be sold. Our main guy was sitting on a throne like seat, offered his card to buy him.

the ambiance was dark , probably had red tones. Both guys were tall , but i especially remember the one being sold was built. It was modern, not historical or fantasy. I only remember this.

Sounds like this https://www.mangaupdates.com/series/52kqkat/mania

that's the one! thank you!

You’re welcome 😉