I connect the laptop directly to the Fritzbox 7490, there are 270 to 300 Mbit / s (in the 2.4 GHz range).
Länderer Chat with Netgear support. Firmware reinstalled, brings nothing. WLAN channel changed in the Fritz box from 1 to 6. Oha! Suddenly 270 to 300 Mbit / s. Back to the original WLAN channel 1 still 270 to 300 Mbit / s. Well so what.
The speed from Netgear for notebook remains below 150 Mbit / s.