To update the Next or Previous text in GeneratePress theme, you can add the below PHP code snippet to your website.
To add custom snippet, you can use the Code Snippet plugin as explained here.
add_filter( 'generate_previous_link_text', function() {
return '← Your Previous Text';
} );
add_filter( 'generate_next_link_text', function() {
return 'Your Next Text →';
} );
Now you can change “Your Previous Text” and “Your Next Text”. The updated text will be visible on your websites front page.