How to reset my games

That probably depends upon the games. If they are still in your country's app store then you can try deleting them from your iPad and redownload them via the Purchased tab in the App Store app on it, but if they are Game Centre games then they might pick up your current progress from your Game Centre account. Do the games themselves have a 'start over' setting on them (either directly in them or in Settings) ?

Have you tried deleting them and redownloading them via the Purchased tab in the App Store app ?

No, you will need to delete the apps from your iPad's homescreens (where you tap on them to open them) : press and hold any of the apps on the homescreen and after a couple of seconds or so they should start to shake, then press the 'x' in the top left corner of the apps that you want to delete, and when you've finished deleting press the home button so as to stop the shaking (if you don't get the 'x' on any of the apps that you've downloaded then check that Settings > General > Restrictions > Deleting Apps isn't set 'off').

As long as the apps are still in your country's store then they should show in the Purchased tab in the App Store app for redownloading.

Do you know how to reset the scores from the beginning for Angry Birds Star Wars on a Macbook? I managed on all my other devices by deleting the app and reinstalling, but it doesn't work on my Macbook.

I don't play that game, but you could try the suggestion on this page (it's a bit old, I assume that the instructions still apply) http://forums.macrumors.com/threads/angry-birds-scores-reset.1104204/ to go into

/Users/"your username"/Library/Application Support/Rovio/Angry Birds

and to delete (or preferably move/rename)

settings.lua

highscores.lua

can I restart my game?