Tyres are made for different vehicles, different driving conditions and for different weather conditions. If you live in the Nordics, you will have to use a winter tyre during the winter season and summer tyres during the summer season. If you live in continental Europe, you may not need winter tyres at all and you will have also all weather tyres as a tyre option.
In the Nordics, everyone uses summer tyres in the summer and the summers are usually not as hot as in southern Europe. In southern Europe, it may be possible to use summer tyres all year around and skip winter tyres or alternatively people can go for all-weather tyres which provide comfortable and safe driving during all four seasons. If you use the same tyre during the whole year, it is important to rotate the tyres every 8000km or when the difference in the tread depth is larger than 2-3 mm. Rotation ensures that your tyres will wear evenly and you can change all 4 tyres at the same time.
For Germany, with their excellent roads for high speed, I would probably select a high speed summer tyre for the summer season and then depending on what type of winter conditions I usually experience, I would either select a non-studded tyre or an all-weather tyre. High quality summer tyres have excellent grip and stability which is what you need when driving at high speeds. The summer tyres also need to be able to handle heavy summer rain and reduce the risk of aquaplaning. Some tyres are better than others on wet surface and preventing dangerous aquaplaning.
The better tyres you have, the better fuel efficiency you tend to get, as the rolling resistance of premium tyres tends to be lower. They usually also last longer, which means that in the long run you will save money. Even though you have high speed tyres, make sure that you drive cautiously and drive fast only on the roads that permit high speeds. The high quality summer tyres have a good traction, reducing the braking distance and helping you stay out of accidents.