Wide-screen Monitor: Windows off screen

Just got this beautiful 49" Samsung Odyssey monitor . . . but while using the 5k resolution, the windows from my M3 MacBook Pro are off (not showing) the monitors screen. If I move the window to be on the monitor's screen, it is off (not showing) my MacBook Pro screen. How do I make all the windows on my MacBook Pro also SHOW on BOTH screens???