germany – Will someone be stopped to leave FRA as a non-German citizen during COVID-19?

I have a co-founder for a startup we’ve been working on and my co-founder is from Estonia. He already has a flight ticket on May 18th, 2020. We have been finding it very difficult to work remotely so he is planning to come here and work together.

Assuming he is able to arrive at the Frankfurt airport, will he be let in? Or will he be sent back i.e. deported back to Estonia? Looking at German airport websites it is not very clear- for instance, Munich airport to me seems like has no issues. Also, currently our startup is not officially registered to issue him any official document.

Also, for the sake of this question, please let’s assume that he is no risk to the current pandemic and that he is traveling because at this point it is almost “essential” for us.