Answers for "css bootstrap image size"

image responsive bootstrap 4

<img class="img-fluid" src="" alt=""> //This will make your image responsive

bootstrap profile picture

<img src="..." alt="..." class="img-thumbnail">

bootstrap image size

.top1 {
    height:390px;
    background-color:#FFFFFF;
    margin-top:10px;
    overflow: hidden;
}

.top1 img {
    height:100%;
}