Check out example codes for "stretch grid column to fit page mui". It will help you in understanding the concepts better.

Code Example 1

return (
  	<Grid container direction={"row"}>
            <Grid item style={{width: '500px'}}></Grid>
			<Grid item xs></Grid> 
			// the bottom one will stretch
	</Grid>
)

Learn ReactJs, React Native from akashmittal.com