The website restricts image sizes to a maximum of 1200 x 1200 pixels in order for them to fit on the screen nicely and to download quick enough, etc.
Most modern phones and cameras take pictures much bigger than this, so you will need to resize them to upload them into your advert.
For a full guide, please see our thread here:
https://www.ducatisportingclub.com/s...ad.php?t=85276 