Images still large after resizing

[#1]

Hi everyone, I'm having a problem with resizing my images to a smaller file size to upload to my blog. I've read many blog posts that say reduce the image quality to 80/70/65 etc and the ppi to 72, which I have done, but my images are still a little high (around 1.3mb).

I want to upload images double the size for retina displays, which is really causing the problem as the images need to be 1340 x 2010. However, I have saved some images from other sites to see what they are doing and they have images that are bigger then mine, but have a file size of around 300kb. How are they doing this? I'm working in lightroom with RAW images from my Sony A6500 (I'm a newbie here). 

Also I have a 4k screen (DEll XPS 15) on my laptop and it says that you need to upload the images double the size for retina, but still have them as the reglkar (half size) on your blog post, in order for them to appear sharp on a retina display, howver when I upload both sizes it still looks the same quality on my 4k screen?

I would really like to learn how to do this in lightroom and not use compressing sites, etc. I have a plugin that compresses images when uploading to blog but they are still around 1mb. 

Any help would be appriciated 🙂 

[#2]

Hi everyone, I'm having a problem with resizing my images to a smaller file size to upload to my blog. I've read many blog posts that say reduce the image quality to 80/70/65 etc and the ppi to 72, which I have done, but my images are still a little high (around 1.3mb).

I want to upload images double the size for retina displays, which is really causing the problem as the images need to be 1340 x 2010. However, I have saved some images from other sites to see what they are doing and they have images that are bigger then mine, but have a file size of around 300kb. How are they doing this? I'm working in lightroom with RAW images from my Sony A6500 (I'm a newbie here). 

Also I have a 4k screen (DEll XPS 15) on my laptop and it says that you need to upload the images double the size for retina, but still have them as the reglkar (half size) on your blog post, in order for them to appear sharp on a retina display, howver when I upload both sizes it still looks the same quality on my 4k screen?

I would really like to learn how to do this in lightroom and not use compressing sites, etc. I have a plugin that compresses images when uploading to blog but they are still around 1mb. 

Any help would be appriciated 🙂