Setting image sizes

I have a problem with the images being uploaded. I want to restrict them to 600px wide. I tried resize-image-after-upload but it does not do anything

I tried css but unfortunately the logo has the same css so it gets resized as well.

.single img {
max-width: 100%;
}

Example: https://thetravelingdressproject.com/listing/northern-california/ where the main image is way too big. I have since added wp-image-size-limit