You should look at it an other way:
Greece and Germany 2 very different countries shouldn't have been part of the same monetary and economic policy system, in this case the Euro.
When Greece wanted to join they had to much debt to be allowed to join by the EU-rules.
So far so good. Nothing bad happened.
Now there is this company in the US called Goldman Sachs which was willing to take on this debt for a number of years in return for a hefty payment.
Greece accepted that offer, which if they really understood the terms and consequences of the agreement they probably would have never done so.
If I remember correct they for example had the interest rate pegged on an index inverse to the GDP of Greece or other similar variable connected to the economy of Greece.
Now after that deal Greece didn't have that large of a debt any more and was able to join the EU.
The terms of the Goldman Sachs agreement said they would need to pay it back after 10 years or whatever but after at that point Greece would not only get their debt back but also a new debt with Goldman Sachs. Obviously Greece couldn't pay that. They probably paid the at least part of the Goldman Sachs debt by getting loans from others. Because the interest of the Goldman Sachs loans was very high especially after the financial crisis.
So Goldman Sachs made a lot of money and had very little risk as the EU would have a big stake in Greece not failing and if the economy of Greece was doing awesome Goldman Sacks would also get paid.
Have a look at the video, you'll probably want to enable the subtitles:
Now Germany and a lot of other EU countries want to put as much of the burden of this problem with Greece, as much as Greece can bear.
Basically about trying to find the right balance:
The people in Greece say: we are suffering enough, our economy is shit and things will get really bad and recovery will take decades.
Germany and other EU countries are saying: you can bear some more of the burden.
However Germany and others are not interested in seeing Greece leave, that would be bad for the Euro.
So the Greece government had some leverage there to force the other EU countries to help them.
As I mentioned at the start, Germany and Greece shouldn't have been in the same monetary system, if they were not Greece would have been able to go bankrupt and just take their losses. They would have recovered much faster from that then being stuck as they are.