I wonder there will be less eggs, milk and butter in supermarkets due to coronavirus. I haven't checked latest situation but on Monday morning, there were no eggs, less butter at a REWE close to my place.
Freezing butter works. I do so before I travel. Taste may be change slightly but then you can use for cooking. I've never frozen milk as it is but I often make white sauce out of milk and freeze it. It works :)
I thought so, that it is because of the half empty shops. Here Rewe and Netto have problems, but if I walk 10m minutes there is a Lidl which so far has no shortages. I also hear its no problem to order online from Rewe, it only needs more time for the delivery. If the situation worsens, I will try the latter...