Please downscale/downsize images prior to uploading. You might want to remove some meta data like location (GPS) too.
The system allows you to upload ...
- max. 4 MB per image (was 2 MB till a few minutes ago)
- max 5120x5120 pixels (was a lot small till a few minutes ago)
The system will then downscale the image to the maximum dimension allowed for you. Please know that the image processing quality is not very good. It will be a lot better when you process the images to the maximum allowed dimensions and size yourself.
The gallery app on Android is able to scale down an image. Have a look at the edit function and the three dots menu. Please use that menu to save a copy after resizing, or you will overwrite the original image.