How to delete game in my account

click it in your game list, click i on the right side, now click folder button. this moves that game to yourarchieve, and doesn't bother any longer in your list

you can archive it in your games

You can't delete a game, but best thing you can do is Archive it

Just for clarifications sake: you can have a maximum of 50 games at any time, including the ones in your archive. Games in your archive will stay there for two weeks and then be automatically deleted for you. They still exist, but you can't access them anymore and they also don't occupy one of your 50 game slots.