Can I change it with CSS?

<style>
/• Style the input box */
#tawk_6492ea7ccc26a871b023d9c3 .tawk-message-form input[type="text"] {
    height: 40px;
    font-size: 16px;
    padding: 10px;
}

/* Style the send button */
#tawk_6492ea7ccc26a871b023d9c3 .tawk-message-form .send-button {
    height: 40px;
    padding: 10px 20px;
    font-size: 16px;
}
</style>