Responsive Section using Flex Box

For testimonials container you can use grid like this : Image

@media (width >= 1440px) {
.testimonials-container {
    display: grid;
    grid-template-columns: repeat(3,1fr);
    grid-template-rows: 20px 20px auto 20px 20px;
    column-gap: 2rem;
}

.testimonials {
    grid-row:1/4; // span rows from 1 to 4
}

.testimonials:nth-child(2) { 
   grid-row:2/5;
}

.testimonials:nth-child(3){
   grid-row:3/6;
}
}