How to highlight text after adding background image

Hi sulabh12. Doesn’t look like you’re using a child theme so try adding the following CSS using a plugin like https://wordpress.org/plugins/simple-css/ or https://wordpress.org/plugins/custom-css-js/:

.entry-content {
    background-color: #fff;
    opacity: 0.7;
    padding: 0 10px;
}

You’re welcome; glad to help.