How to display the full text of an article when using the_excerpt?

Question

WordPress

I ask you not to swear in advance at the possible simplicity of the question, and I will warn you that I spent quite a lot of time looking for an answer so as not to litter the forum.
I am looking into creating themes for WP. I need to make a short "announcement" of the post with the "read more..." button, I googled this way:
In the post, in the "excerpt" field, I write my announcement, in index.php I put the_excerpt() and write the_permalink() to the link. In all guides, when you click on the link, the full text of the post opens, but when I click, the announcement continues to be displayed.
Tell me how to fix it? Or where to read about it?

Answer 1

Are you probably using index.php to display posts as well? If so, copy it to single.php and replace the_excerpt() with the_content().
Or, in index.php itself, do a split:

if( is_single() ) {
    the_content();
} else {
    the_excerpt();
}