How can I restore all files i deleted in the Applications floder?
Without being at the helm of your computer, I would advise a fresh installation. Reboot into recovery mode and reinstall OS X. This should restore all system files, and your personal files should not be effected.

You can boot into recovery mode a number of ways. One would be to hold alt at boot, then select your Recovery HD. In some instances, an OS X user may not have this drive. Instead, you may want to try Command+Option+R for Internet recovery.

A program like PhotoRec, which comes bundled with TestDisk. http://www.cgsecurity.org/wiki/TestDisk_Download

It runs in Terminal, but you would be able to select your drive and recover all files. Note that any files that have been overwritten since they were deleted (which is very likely) will not be recoverable.