can't download apps

Hi, I have a big problem right now and I can not find any answers in the forum so far.

I bought my MacBook Air in Switzerland because I used to live there. Right now I'm in Peru for a couple of years but a few weeks ago I wanted to update the Mac OS to El Capitan so I used Time Machine to back up everything. Or so I thought...

After the update - so far El Capitan works great- I started copying all the files I needed back and that's when I noticed... Time Machine didn't back up my apps - like Pages, Scrivener, etc- and all the books I had in iBooks are missing too.

I had to change the Apps Store once I moved to Lima but until a couple of months ago I could always go back to the Swiss App Store and update my apps, but I can't do it now! I always chose the "None" option when choosing for a method of payment but it's not available anymore... What can I do? I don't want to lose all my apps, specially not Scrivener. And I certainly don't want to buy all the apps again.

Please, I'm desperate for help, can anyone give me some advice?

Thanks in advance.