As far as I am aware, DreamHost only accepts payment is US dollars. However, if you make the purchase using your credit/debit card or PayPal, the currency transfer will be handled automatically.
I am not 100% sure I understand what you mean here, but when you upload new content to your websites, the changes will be immediate. That is to say, the files you upload will be the ones served by Apache from the moment you upload them.
There was a period when the DreamHost panel was extremely slow, but things have improved greatly over the last couple of months. The panel can still be slow(ish) at various times of the day, but not slow enough to prevent you from getting something done.
DreamHost has a team actively working on improving the response time of the panel, and I expect things to keep improving over time.
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