Hi there! Sorry you are having troubles with the Classifieds.
One simple way to get around problems like you are experiencing is to write the ad in sections. In other words, don't try to post the whole magilla in one go: break it down.
Go into the Classifieds, and after confirming you are logged in, create your ad, but only put the minimum info and no photos. Save the ad, then go back in and add more, let's say, the description. Save, open the ad in edit mode again.
Now try some photos bearing in mind that many users have trouble posting photos larger than 600 X 600 pixels.
Let us know how that works?
On behalf of
The Site Team