Start by measuring your available space—aim for a desk 100 to 120 centimetres...

https://www.bookmarking-planet.win/planning-a-gaming-setup-in-limited-space-starts-with-choosing-a-desk-about-100

Start by measuring your available space—aim for a desk 100 to 120 centimetres wide to fit your gear comfortably. Use a monitor arm to free up desk surface and create more room for your keyboard and mouse