Hey, i know that this is a stupid question, but, how can I fix this: http://prntscr.com/aqm9wc ?
Do you mean the square gridlines? Try building the lighting. Or your snap to grid value might be super high
looks like a landscape to me, if so… you should try following the docs:
https://docs.unrealengine.com/latest/INT/Engine/Landscape/index.html
or some other tutorial. just google it.
you have to apply a landscape material to get those to go away & best to know how first. 
Build the lighting or change the directional light to ‘moveable’ 