Basic problem: CMS multi-picture light box overrides other sections

Good morning friends, I am a novice in web design and I have a problem.
I’m sure it’s something very basic and elementary, but I’ve spent several hours and I can not solve it.
Please help me.
I have a CMS where I have a section of multi images, at the time that several images are uploaded, they override the subsequent sections and images.
I do not know if the problem is in the Z-Index or something. To say that the web does not have CSS added.

Any help is appreciated.