Missing continue reading button

Hi. I’m sorry to post a topic after another but I’ve got a very bad problem. Full posts were displayed in the homepage instead of showing just a paragraph with the “continue reading” button.

There was a user with my exact issue and he was told to add a code in the functions.php file. I did it and it basically worked but… Posts are now showing without the “continue reading” button. But the biggest problem is that every time I open an article to fully read it, I can see only a paragraph. The rest of the content is lost.

Please let me know hot to solve the problem. Thank you.