My website too slow?

It has been only 2 days that I’m using this theme (and I am using it in WordPress.com Premium, I hope you can help me anyway).
Me and my coworkers see that the website is too slow, it takes too much time to upload when you change to another page.

Is it the theme that is not ready to work to have so many pages? Os I might have put too many information? Note that all the images are just the size that is needed, not more.

Hope anyone can help me;

Thanks a lot !