Setting sections to 50% width and centering things vertically

Hi there
I've got a pro version. I'd like to set sections to 50% width, so e.g. "Woda" section would be on the left and "Scieki" would be on the right, both of them taking 50% of the content width. I've tried everything that I could come up with, nothing works as it should, please help.
And second question is how to position the image in the middle of section vertically, regardless of how long it would be? The display: flex doesn't work here as it seems to damage the overall structure. I've tried to do that with text also, but it doesn't work either.
Thank you
k