Please help, I have several issues [Questions on the use of Adobe Portfolio]

I have been making a new website using Adobe Portfolio.   I struggled through it and have put together a pretty decent site considering I had no idea what I was doing and it took me a week of working on it every night. I have several kinks I can not figure out.

#1 how to create captions for the art either in the grid form or the enlarged form.

#2 How to make the background black or dark gray on the enlarged version of each image. I don't like that white background.

#3 How to get an image to show up when I share the link as below.

#4 How to change the background on the enlarged photos black and how to make the site “secure”

#5 How to change the cover photo

Thanks in advance.

http://www.marshaslopeypaulekas