Formating stopped working correctly

Hello team,
I have one quite strange problem. I’ve tested a new theme, I wanted to put on my site. But after it didn’t work, the formatting of tags, categories (in index.php file of the theme) stopped working correctly. For example, I’ve replaced the […] with a “Read more” link. The link is still in formatting.php, yet the excerpts show […]. Also, if I lower the value of 55 in formatting.php, the excerpt remains with the same length, as if I haven’t changed anything. I really hope you could help me.. thanks in advance!!