Thanks for providing awesome theme that Activello is.
In Activello, when you open from mobile the nav menu is compacted into a dropdown list. I currently have a problem where the transition when I click the dropdown nav menu is not smooth. You can see something like a glitch when you click it.
I tried to disable all my plugin but the problem persist. The URL for checking this problem is zharasonline.com
It seems this is happening on your site because loading child theme style.css file twice in your site as shown in the attached screenshot.
To confirm it just temporary use the Activello theme instead of child theme on your site. If everything works fine then it’s your child theme issue so just share me your child theme so that i can troubleshoot it.
You are right, I troubleshoot myself and I found that at the end of functions.php in my child theme folder, I put “?>” delimiter, when it shouldn’t be there.