Style Cart and Checkout Page Title

Hi there

try this CSS:

.woocommerce-cart .entry-title, .woocommerce-checkout .entry-title {
    text-align: center;
}

So, simple! Many thanks, David :)

You're welcome

Just one additional question. Now it's too big on mobile view. How can I make it smaller for that?

The entry title uses the Customizer > Typography > Headings > H1 settings.
If you want to control it separately then this CSS:

@media (max-width: 768px) {
    .woocommerce-cart .entry-title, .woocommerce-checkout .entry-title {
        font-size: 28px;
    }
}

Thanks for your support :-)

You're welcome