Position of text

Hello, thanks for this wonderful theme! I installed this theme a week ago and now I came across the following problem:
When I see my website on a big monitor, the text of the sections below appear in the part of the background video. This also happens when I zoom in on a smaller screen.
Where can I change this?
Also when I click on a link in the menu, it doesn’t precisely hover to the section title.
How and where can I fix the position of the text?
The link to my website: https://wangxiao-music.com/
Thanks in advance.