Someone stole my game

You'll need a lawyer local to your area that can help you go through the process.

The details will matter. If you registered the trademark and the copyright for the game matters, although you technically have many rights automatically, other rights require government registration.

What you have rights to do and the ability to enforce without court order will depend on lots of details. With a lawyer it can be straightforward to issue a takedown order to Steam or other distributor if you meet certain requirements, but if you don't meet the requirements they won't matter at all.

Details of who infringed will matter. If the company is a cloning company out of China, Taiwan, or South Korea, the cost of fighting them internationally quickly balloons to the point where it isn't worth it. You may get successful takedown orders on Steam, Epic, and the Google/Apple App Stores, but sites like Kakao Games or WeGame or MyApp are unlikely to take it down unless you've got a legal order from Chinese courts or have registered the game and the assets with the Chinese NPPA.

Recovering legal damages through the courts is an expensive process, and it usually isn't worth the cost of battling in the courts, but if you're looking a minimum range of several hundred thousand dollars to millions of dollars in damages it can be worth it, but if it's only tens of thousands of dollars enforcement will likely be more expensive than you'll ever recover.