Why The Background Image Does Not Fill The Entire Div

I have the following code which displays a SPAN inside a DIV and then another DIV under it which displays some texts. The issue I am having is when I resize the browser the texts a

Solution 1:

Use background-size: 100% 100% to fill completely (maybe stretched) other wise use background-size: cover as @Andras said

Solution 2:

Use background-size:cover, and it will fill.