Thanks for contacting us.
1> Please go to Theme Options > General Settings > Back To Top: On to turn on back to top button on your website. You can refer this documentation for more details:
2> You can give us exactly the link that you want to change the size of "sale" and "90%" tag.
We will help you to add Custom CSS segment to change.
3/4/5> We have checked demo menu > it works fine. Please check again then give us your website's URL, we will check it directly.
Please check, then feedback to us soon.