heavy plug in?

I love the plugin and that unlike others its free, so i really appreciate it. However it makes my page run more slowly.

On my landing page I have only short text + twenty20 before/after photo.
and that page is the slowliest. The photos are already compressed so the size should not be a problem, so the speed, especially at this page with nothing else on it.

I wonder is it just my theme, or is it general issue? Any fixes for this? Also i had an issue, that I could not change the size of the photos. at some point, the photos were huuge, so person had to scrol to see it all. It fixed, when I changed ”layout page size” But.. i still wonder it there is some CSS for sizing?

PS: i am on theme BRIDGE. I would not reccomend this theme to my worst enemy, since its very heavy [so waiting for better times and developer to change it so it looks same but with better responsive theme] so yes, regarding the speed issue, the Theme is 90% at fault, but the speed got even worse with twenty20.

Thanks