Is a vacation for 3 weeks in Germany really expesive?

because i converted my 5 thousand $ into euros and it went to 3 thousand euros
so is everything over there expensive?

If you're smart you can travel anywhere in the world on the cheap. Germany is no different.

Example: There's a pizza shop in Nurnberg that sells espresso for one Euro. Around the corner and in most places nearby a very similar product costs 2-3 Euros. Another from the same city: The famous three sausages on a roll sells for 2 Euros at a stand on a side street, while other vendors charge twice as much around the corner.

Follow the locals and you're generally on the right track. Learn some German and engage them in non-tourist areas. Ask for help finding what you need. Be persistent if you are brushed off (which is unlikely; many Germans are wonderful, warm people). Be fearless, inquisitive and respectful. A smile goes a long way in making international friends, who are the most precious travelling "commodity" out there.

No it's all to do with the exchange rates at the time, the price of things over there reflect the inflation as do all countries. But because of the exchange rate if you work the price out in $ it might seem more.
With a thousand euros a week though, you really shouldn't run out.Obviously it depends what and how you spend your money and where in Germany you're going.
I went to Berlin for 10 days and took just over 800 euros and I managed just fine!
Hope you have a great trip!