If I go back to an auto save before the collapse and war with Germany will everything happen again? Will Germany still declare war? Next time I won't keep the cities I'll just wipe them out. I had to fight, Germany gave me no choice and didn't want Peace.
Yes, it is likely (though not definite) that Germany will declare war on you again if you do that. But I wouldn't recommend wiping out too many cities, since each city you raze takes away stability points. If you have to fight Germany, try to play a defensive war. Destroy any units they send toward you, but don't launch any attacks on their cities (or if you want to just to kill some of their units, make sure they still keep the city). If you can, drag someone else like France or Russia into the war on your side. Eventually the Germans will get tired of fighting you and will accept a peace deal.
How do you boost your Economy? What buildings do I build in my cities that help the Economy?
You want to build granaries, courthouses, markets, grocers and banks in all your cities. Also, building lots of cottages on your grassland and plains tiles is a good idea. There aren't any technologies or wonders that will directly improve your economic stability. Read the
"Economy category" section of the stability guide for a list of what will help and what will hurt your economic stability.
An important part of it is growth. You want your population, agriculture and industry to grow. You want your cottages to grow into towns. If you have to conquer more land to increase your population, try to take land that Greece historically owned in the past (there is a map
here). You'd be much better off conquering Turkey, Persia or Egypt than Germany or some other European nation. But don't expand too much or too quickly.
How long does a Plague last? I never seem to survive one. My cities eventually change to Independent after several turns.
It varies, but they usually last about 4-9 turns. Make sure you have enough units in each city so you still have some defense after the plague takes its toll, and try to have aqueducts in all your cities. Also research Medicine ASAP, since that technology will make your empire immune from all future plagues.
What are the best Civics for good stability?
It depends on what civics you have available at your tech level, and what you are trying to do with your empire. Basically, certain combinations of civics work well together for your stability (like Representation + Bureaucracy, or Emancipation + Free Religion) and some combinations are inherently unstable (like Emancipation + Theocracy, or State Property + Vassalage). Read the
"Civics category" section of the stability guide for more info.
But try to change your civics as few times as possible. Every turn of anarchy gives you a permanent stability hit. It's best to change civics only two or maybe three times before you discover Radio and build Cristo Redentor (which erases the anarchy between civics changes).