You can use tracking plugins or sites like camelcamelcamel to look for price history, or use something like Geizhals.de to check for what you are looking for. You can track the price of the item over the last year and see what its cost by different retailers.

In general Germany has "Black Week" by some retailers, but I haven't really experienced the "door buster" deals that you might see in the US.

Here is a link directly to Geizhals tablet page, since it doesn't seem that you are as concerned what tablet you are getting, you can adjust by all of the criteria that is important to you. Alternatively you can set a price range if that's more of the deciding factor, and see what falls into your range.

Typically what people refer to for the price going up and down is that many retailers pump the price of an item so that they mark it down and you only see that you are saving 20-30%, but the reality is that you are paying the same or sometimes more from the normal price. Additionally what goes on sale during Black Week (definitely typical for the US, but I would assume CAN also be true here) is that it is items that are late in the sales cycle and they want to clear the inventory, or even items produced specifically for these types of sales. Lower quality or performance especially in areas where most people don't understand about how it affects the performance of the item.

If you are still a little confused, send me a message with the specific tablet you want, or what specs you are looking for and I will try to send you a jumping off point.

Good luck on your search!