problem with mobile display of a webpage

Hi! I am currently finishing a Coursera specialization, web design for everybody. the final project is writing a portfolio. My projects is mostly done, but one of the pages seems to have a problem when displayed in a cellphone. at some point, everything gets hidden. its just white space all the way down. that problem only appears in the cellphone, not in “inspect mode” using chrome for desktop. I cant figure out what the problem is… can anybody help me?

the site adress is

thank you!

this image is a screenshot of the place the white begins.