If the files uploaded are images.

If the files uploaded are images... is there any way to downgrade the resolution so it will fit to these limitations automatically?

Unfortunately, the file upload field doesn't have the feature to reduce the image resolution.

You may try using the https://www.jotform.com/widgets/file-uploader-by-uploadcare  widget which has the option to reduce uploaded file size.

Hope this information helps.

If you have further questions, let us know.