grid container min and max width?

Hello, I have a grid-container that has a background color, but upon resizing the browser the grid shrinks, however the items stay the same. my code for the grid to stay the same size is:-

min-width: 620px;
max-width: 620px;
Now it doesn't move which is ideal but probably not how this should be done, does grid container have an simpler way of fixing the movement in place?

I've now gone with

.grid-container2 {
display: grid;
grid-template-columns: auto auto auto;
gap: 10px;
background-color: #2196F3;
padding: 10px;
max-width: 75%;
}

Would that be good coding?