I'm living in Germany right now and have realized last week that I need to declare my taxes. I am married and have a wife. In 2015 I did not work and married my wife in march. she is not a citizen or resident. In 2015 I did not work but my wife worked. Do I have to Declare taxes for 2015 even though I didn't work but my wife did? At the time I married we both lived in Germany and pay German taxes.
U.S. citizens generally have to file taxes every year regardless of location. This is unusual - most countries don't require this.
Assuming you are a U.S. citizen talking about filing U.S. taxes, and you made enough income to require you to file, you would do well to go to the IRS website immediately to file forms to request an extension, if that's still possible. ...
Why are you asking about 2015 taxes in 2018?? If you have not even filed taxes for the past 2-3 years, you might want to seek the advice of a tax attorney. If you're a U.S. citizen, regardless where you live or who your spouse is, you need to file if the total of your income earned anywhere exceeded a certain threshold and wasn't already taxed.
Whether to file jointly or individually is best answered by a tax attorney. Filing jointly could help you establish your relationship timeline & validity if your wife decides to apply for residency in the future, but it's not mandatory. Do whatever makes the most financial sense for your situation right now.
Whether or not you have to pay taxes is a separate matter. If you earned no income (which might be difficult to prove - were you a student? Did you collect unemployment?), or if you already paid German taxes on 100% of income earned abroad, you shouldn't have to pay U.S. taxes as well. You most likely have to file every year unless you made almost nothin. Note that there may be things like unemployment, social security payout, or other benefits that could potentially be considered "income" so you should speak with a professional.
You are required to file, but you probably don't owe any tax as your income is probably below the maximum amount of the foreign earned income exclusion. I was in a similar situation and just mailed a few years' with of tax returns together and it was no problem. I used Turbo Tax to do the current year, printed out the forms and used those to help me fill in the previous years manually.
It is of critical importance though that you do your foreign bank account reporting and catch up on previous years if you have not been doing that. The penalties for not doing this can be severe. In my case, I didn't realize I had crossed the threshold requiring reporting them so I also did a few years at one time and included a letter explaining why I was late filing. I never heard back so I assume it was acceptable since I was a small fish.