There are some reasons that cause your section be bigger than you expect and may cause overlapping, white space on the bottom of the section on so on...
Use the following checks to find what can enlarge it and resolve the problem:
1. Check you section size at the Inspector panel, it may have min height
2. Check the grid settings (row height) and make sure that it is not bigger that you need
3. Check if the objects in this section have min height or min width that is too big for your section
4. Check object margins. In case they are too big, they can cause the section to enlarge and create an unexpected horizontal scroll
5. Check that the object margins have no minus value. It causes the object to be bigger than the section