Where does scrolling come from when adapting?

Question

css

f0186535.xsph.ru/one.html
Where does scrolling come from when adapting?

https://jsfiddle.net/daft82m5/33/ "

Answer 1

You set both 100% width and margin-left for .language and .item-menu
When adapting, either remove margin-left or immediately set this indent using padding

Answer 2

You have everything indicated in pixels, specify in percentages