Hi, thx have made this, 

i installed post blocks for elementor, and when i put it into the paper of elementor, it showed that it has underlined title, but after i tried to turn text decoration to none, it doesn't change at all, so it stays having underline, so how do can i fix it ? help pls

yep i do, thx for reaching out, by the way ive got it, finally i put this css code to custom css in its elementor this :

.ast-single-post .entry-content a, .ast-comment-content a { 
    text-decoration: none;
}

which this .ast-single-post .entry-content a, .ast-comment-content a i found on its inspect