Thank you for your answer, and sorry for my mistake, first time posting something with Codepen.
Here is the link to my issue, hope it will help.
So to make things clear, when I put my h1 tag outside of my section, the code works perfectly, but when i put it inside the section you can see what is happening.
https://codepen.io/bogdan-stojanovic/pen/GRLdoVN