Zu niedrige Leistung iPhone 7 128GB Antutu Benchmark

In my opinion those benchmark apps are not accurate either. You would have to set the phone back to factory settings, with no other apps installed, to find out, if the app shows accurate results. And you don't know how those other tests were made.

Restore your iPhone, iPad or iPod touch to factory settings

My suggestion, if you think that your iPhone has a performance problem, get it tested by Apple and not some 3rd party app.

If you think that your device has an issue, you should get it tested by visiting an Apple Store or Apple Authorized Service Provider next to your place. Apple has their own tests to verify the performance.

And, I found this interesting comment in a review of Antutu-Software:

Benchmarks aren’t perfect and don’t exactly mirror real-world use. Some manufacturers may optimize their devices to perform faster in some benchmark apps — effectively cheating the benchmarks and making their phones seem faster than they are. For example, a phone may run a benchmark without slowing down its CPU like it would in normal use. The benchmark wouldn’t represent real-world use, but would appear faster. Benchmarks like AnTuTu do measure real performance, but you have to take them with a grain of salt.