Why did the elements shrink?

Question

css

Here is the original how it should look like https://dwstroy.ru/lessons/les3397/demo/index.html
Here is how my menu shrank
Why did it shrink?
PS I did everything perfectly on a clean file. When I transfer it to my site, it compresses. Why? Thanks in advance

Answer 1

The problem was in bootstrap

Answer 2

Let's guess without code example! style file rules. Show live code.

Answer 3

The contest of psychics is declared open!