Hey, a bit late but my girlfriend visited me from Ukraine several times already since they published the exception for life partners last August. You need a declaration signed by both that you have an ongoing relationship, copy of passports and a signed invite by the German resident. I highly recommend bringing along a bit of proof for the existence of the relationship (just in case), e.g. pictures, facebook entries or so. Especially some proof that you met before (e.g. flight tickets, passport entries etc). Once in a while airport police is not aware of the exception, they then need to check with their superiors usually. Depending on the airline they might check all that stuff already before your departure at the airport. Don't forget a proof that you are health insured during your stay as well as the digital pre-registration. In her case they always checked on that.
P.S.: it no longer matters in which country you first met (they even didn't mind before that was officially put into place, they only cared that we met physically before the flight restrictions came up).