Original aspect ratio - Portfolio Thumbnails / Inject a font /Make images pass under header

Hello, Im looking to add code for the following items on the test site Im building out.

Heres the test site I am programming:

https://polygon-coral-2kxs.squarespace.com/

Password nep2.0test

These are the items I'm looking to solve for now. 

-Add a custom font into my site for all text.

-Make my images scroll under my header -  text show over images.

-Example: https://www.nathanperkel.com/

-Make the thumbnails for my portfolios show original aspect ratio like my other galleries. Example: ( https://polygon-coral-2kxs.squarespace.com/portfolio-2 )Want to keep name centered below. (Want this and all text to be my custom font

Replicating this site: https://www.nathanperkel.com/

Thanks!