Changing squarespace template

Hello! I have a squarespace site that I have been using for a year and I wanted to change the template for it to have a different layout and feel. I attempted to change it to the Flatiron template bc I love the look of the landing page. I realized after changing the template that now my site is a little screwy. I would like to consult with someone the vision I have and find out how much times it could take to get that done.

Thank you!
Jasmine