We filed in both countries for the year we moved, and it took most of the following year to finish. The German side wanted proof of what we'd earned in Egypt before arriving, because it affected the rate on the German income. I didn't understand why until an adviser explained it. We used one adviser in Germany who had worked with other Egyptian families, and she coordinated with a colleague in Cairo. That was worth every cent.
Something I wish I'd understood before we moved: the year you move, you can end up dealing with two tax systems at once, and they don't necessarily agree on when your year starts, when you became resident, or which income belongs to which country.
In our case the UK has a way of treating the year of arrival as split, but only if you meet certain conditions, and India's tax year runs on different dates. My accountant sorted it out in the end, but I spent a lot of evenings on it before I gave up and paid someone.
How did others handle the year of the move? Did you file in both countries? Did anything get taxed twice before it was sorted? And did you use one adviser who understood both sides, or two separate ones?