If or/and statement advanced custom fields [closed]

I believe you are on the right track with your second idea there, but you have some syntax errors with your conditional. In PHP all of your logic should be wrapped inside one set of ( ) for your conditional. Try this:

<?php
if ( get_field('website') || get_field('emailaddress') ) {
    ?>
    <footer>
        <?php
        if ( get_field('website') ) {
            ?>
            <a href="https://wordpress.stackexchange.com/questions/157835/<?php the_field("website'); ?>"><?php the_field('website'); ?></a>
            <?php
        }
        if ( get_field('emailaddress') ) {
            ?>
            <a href="mailto:<?php the_field( 'emailaddress' ); ?>"><?php the_field( 'emailaddress' ); ?></a>
            <?php
        }
        ?>
    </footer>
    <?php
}