Image not displaying correctly

I know there’s a lot of forum posts about image compression and I’ve honestly tried lots of the recommended actions. However, I still can’t figure out why this keeps happening.

My images on the front-end do not display the correct size and resolution. My images look okay on the post editor and for some reason, the featured images are also very crisp. The content images seem to be smaller. I also tried to check on a localhost/wamp and when I did, my images worked totally fine on the front-end (I’ve used the same theme on localhost and live site). So I have no idea why. Is it my browser? Is it wordpress? Here’s a sample post: https://cameraandcheese.com/that-ginsiyaman-weekend/.

Please help me. I’ve been at this for more than a month now. I thought it was my theme. So I made a new one and still no luck.

Note: I designed my theme based on Underscores and I’ve installed Bootstrap.