我的我的UL列表（列）是我在css中写下的下拉菜单吗？

I have a dropdown menu in html/css with 2 nested columns. When the top UL list is hovered, the second column being displayed on top of the first column. The behavior is strange because each nested UL is created separately and directly displayed on top of each other. Therefore the only 2nd nested UL is visible, with exception of the last the last LI of the first nested column. I have a dropdown menu in html/css with 2 neste