Antonis Samaras told Thursday's Süddeutsche Zeitung that much had gone wrong in Greece but it was determined to change its ways and would fulfil its commitments for €11.5 billion ($14.2 billion) of savings.
The interview, a copy of which was released in advance, will be his second to appear in a national German newspaper in two days and precedes his visit to Berlin to meet Chancellor Angela Merkel Friday.
"The Germans will get their money back, that I guarantee personally. And all the others will get their money back too. We will fulfil our commitments fully," Samaras told the paper.
He had told Wednesday's Bild newspaper that Greece needed "a little breathing space" to make spending cuts and reforms to unlock more funds.
In his latest interview, he called for "a bit of light at the end of the tunnel" and did not say whether he would discuss a two-year reprieve with Merkel at their talks, but reiterated Athens was not asking for additional cash.
"We will deliver. Greece will change and we are determined about that," he said but warned against scaring away investors in his country, which is in its fifth year of recession, with talk of it leaving the euro.
"Every time a German, Dutch or Austrian politician raises our euro exit, I think 'how am I to privatise state-owned enterprises? What businessman will invest euros in us when maybe he'll get drachma back?'," he said.
As part of a rescue package with its international creditors, Greece has committed to slashing some €11.5 billion from spending over two years from 2013.
A team of auditors from the European Commission, International Monetary Fund and European Central Bank is due to report next month on whether Greece has done enough to unlock a further tranche of aid to stave off bankruptcy.