How to add *** between posts, how to remove POSTS?

It doesn’t look like you are running Twenty Seventeen, you are using the Bento theme.

Go to Appearance → Customize → Additional CSS and add this rule:

.home .hentry:after {
   content: '***';
   font-size: 22px;
   display: table;
   margin: 0 auto;
}

Not sure what you mean by “removing posts,” though. You want to hide certain posts on your home page, or do you want to delete the post altogether? If you want to delete a post, go into the post editor and click the Move to Trash link.