Hey all, I just wanted to post this, as it might help some of you that might be struggling with this topic.
When uploading images to your WordPress website, we recommend a small image size, whilst bigger photographs will cover more of an area, they really do not need to be any bigger than 700px on its widest side, personally I use up-to 900px wide and for a cover image 1920px on its widest side, but everything else just needs to be smaller, especially if you have a slow website or web host, you need to think of the people who are going to look at your website, the bigger the images, the slower it will take for your website to load.
This is the image size we are looking for ideally.
When you import a photo, its likely to be a high resolution as seen here (1999) we need to make some changes.
There thats a lot more better, I also like to lower the quality from 100 to 50% quality.
I really hope this helps and if you have any questions to please let me know.