Hi Deborah

Thanks for reaching out in the community. I don't think that the swim-lanes are overlapping but instead I think that there are three swim-lanes shown in the screenshot. If you drag the third horizontal line (from top to bottom) you should be able to drag that down to contain the desired content. You can resize the swim-lanes by grabbing the bottom horizontal line and dragging it up and down. If you select on the swim-lanes at the top of the editor you can determine how many lanes you would like your diagram to have. I hope this helps. If you are still having issues please fill out this form. 

Perfect that was it thank you!