Comment section

Hello! I read everything I found on this but they dont work.

1. I wish to delete the subtitle lines in blog comment section. I dont have a child theme, I would need a css that I can insert to general styling. And which works :)

2. I wish to change the title line in this section, but I dont dare to change anything in function.php.. Is there an other option to do this? And if no.. Okay.. how do I do it in function.php?

Thanks a lot in advance!

Anna