CSS multiple Title creation file on Magento 2

I have a Magento 2 site with multiple classes for different pages and want to create some unique classes for have a more uniform look to site. I already have all info about sizing but need someone to create those classes and attribute them at the right places. I also need to have css modified so it change Header image according to desktop, tablet or mobile for optimizing look again. I aslo need to adjust some css to better align text on site. My custom css file is already created.