i mean all images i uploaded are limited to 1600px.
Unfortunately, I still don’t understand what you mean.
What’s making you come to this conclusion? Can you provide a screenshot that shows uploaded images being limited to 1600px?
As I mentioned earlier, WordPress will always upload your original size (or give you an error that it’s too large and it can’t upload). But the exact size that’s displayed on your site depends on the context the image is being used:
1) When you insert an image into the post editor, you have the option to choose the dimension/resolution you want to use. As I mentioned earlier, WordPress automatically generates some thumbnail sizes as defined in your media settings, but themes and plugins can also define additional sizes to be generated.
2) In automatic post listings on your site, our theme (or a 3rd-party page builder plugin) will define various thumbnail sizes to be used in different contexts.
3) Plugins that create their own content pages may also define the sizes of images for their archival listings.
In all cases, the original image at the original dimension should be uploaded and remain intact.