What should be done to make that lower block wrap around blue (without the float property)?

Question

css

This should be done with the help of "FlexBox " Desirable
: Two blocks (or more) that should be side by side should be in the same box (preferably give a class or id, We will give class = "primer" for example), and those that should be with top or bottom (header/footer) must be separate.
And in css you need to write the following to the primer class:

.primer {
 display: flex;
flex-direction: row;
}