How long should I wait to hear back from an internship?

I am a Ph.D student and had an interview for 2019 Summer internship on Nov. 7. At that time they said that I can hear back by end of Nov. But there was no response, so I emailed them on Dec. 3. They responded that one more extra week is needed.. Now It has been two full weeks since I got this email, and I am wondering how I should proceed? Should I email the company again to reaffirm my interest a second time or should I be giving up on this opportunity? When I was interviewed, they said I am the strongest candidate and they have a project I can participate in. They also asked me about longer internship for Summer and Fall, and I definitely answered yes. But I am so confused due to no responses at all. What should I do?

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