Hi,
Loco translate > Themes > XStore > add the language you need https://gyazo.com/fed3dee6ba549640ff5bebd06f5b4ccc Translate the necessary strings.
Do the same for the XStore core plugin (Loco translate > Plugins > XStore core).
Also, don’t forget to choose the site language in Settings > General.
You can change the popup checkout button color and background by adding following mentioned CSS rule in additional CSS by going to Dashboard > Appearance > Customization > Additional CSS
.woocommerce-mini-cart__footer-wrapper a.button.btn-checkout.wc-forward {
background-color: #000;
}