How can i get my iPhoto pictures back, when they are all deleted?
First: Nothing is lost. Yet. It is only hidden from plain view.

Next, the file and menu names below might not be correct. I am doing this from a German OS, and I did not want to reboot just for the filenames.

iPhoto keeps your photos in a subfolder, named "iPhoto Library" of the "Pictures" folder in the user directory. You need to control-click that folder (it actually looks like a file, but it is a folder, trust me!)

Then you will see a popup menu, and the third entry from the top ("show database" or something like that) is what you need. It will open the folder and display its content. One of the subfolders is called "Database", another is called "Masters". The Masters folder contains more subfolders, one each for each year of photos. Inside you will find subfolders for the months and inside again for the days. There you will find all your unchanged photos. If you rotated, cropped or modified them in any way, those photos are in the Database folder. I can only encourage you to explore them and copy all what you want to preserve to an external drive, so it can be added to iPhoto again.

But please fix the cause of the slowness and the crashes first! If your hard drive is dying, make a full copy and work on that to recover your photos.