Dear Nicepage My website www.darthinu.com has a lot of bugs? The CSS styles are all wrong. Please help Thank you Jayden

Modify for the following CSS classes in the header, as those generated by Nicepage Desktop break the layout when clicking on the mobile menu: .u-header.u-sticky, .u-offcanvas-opened...

No problem with adding custom CSS code until now, but it seems that the code I'm adding is being deleted / corrupted. I copy paste the code in "edit css" window when I open it again there's only one...