Dear Dr. X,
thanks for your kind interest in our research!
I am impressed by your research record and consider to proceed with your suggestion to host you in our group provided the financial situation from your side is secured.
What are your plans for this one? You mentioned the Humboldt foundation as a possible source. I have no experience with this organization on this fellowship level.
In terms of being integrated in the group very good communication skills in spoken English are essential.