get rid of the underline first 3 letters of the sections in the Info tab

Your guidebook is using Guidebook 2.0 (you can tell because of the bottom tab bar: Home, Info, Assistant). In this design, the first few letters of section headings are intentionally underlined in the guest view. It’s part of the visual styling for those accordion-style topic titles.
So this isn’t a formatting error or something you did wrong — it’s just how the current guidebook design displays those headings.