AS SSD should be in whatever language your operating system is set to (I see English when I open it). But it does have a Language menu with both English and German in it...
When using benchmarks like this (benchmarks that perform write-testing), benchmark sparingly
. If you do more than like 3-5 in one day, then you will notice a decrease in performance. But it's all good because TRIM will take care of it. I think you'd just have to give it time.
Speaking of benchmarks that perform write-testing, I recommend ATTO Disk Benchmark
because it'll show you results that are closer to the advertised speeds. Benchmarks like AS SSD will only let you see results that could be considered "worst case scenario".
But for a great benchmarking program that doesn't perform write testing, use HD Tune 2.55