ITEMS ON THE PRODUCT PAGE

Hello @mirek128,

You can use the woocommerce_after_add_to_cart_button hook. :‎)

For example:

function add_test_text_after_add_to_cart_button() {
    echo '<p>Hi, I\'m a test.</p>';
}
add_action( 'woocommerce_after_add_to_cart_button', 'add_test_text_after_add_to_cart_button' );

Link to image: https://d.pr/i/4MDsKk

You can find a visual representation of the single product page hooks at https://www.businessbloomer.com/woocommerce-visual-hook-guide-single-product-page/#actions.

If you require the assistance of a developer, consider hiring a WooExpert.

Cheers!