Photobucket is the problem. Especially with recent changes.
Posting pictures was never easy for me either until I created an account on "Imgur." Totally free. No nonsense.
Click on "albums." Create a new album. Leave the setting on public so you can share pictures.
Click on the little green down arrow to the right of auto resize. Click on 600 X 480.
Next you can drag pictures into your album or just hit computer and go to you picture file and individually select pictures.
Open a new page on your computer and open up Tradgang. Click on New Topic at the bottom. Then go back to Imgur and click on the individual picture in your album that you want to copy to Tradgang. Above the picture you will see "BB Code message board and forums." Copy the code below that to your new topic on Tradgang. When you save your new topic on Tradgang, the picture will be there correctly sized.
If this sounds difficult, its only because I have done a poor job of explaining it. I'm an idiot on computers, and I figured this out on Imgur on my own. But photoshop is totally confusing to me.
Good luck!