I used the Wifi Analizer app. This app told me to change to chanel 13. Later i read that chanel 14 an 12 also have to be totaly free for transmission, if not, it is better to configure wifis to the same chanel, so they can take care to each other. After recofiguration wifi works better, also connected 1 device with cable with following results:
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-20.00 sec 112 MBytes 46.8 Mbits/sec 4 sender
[ 4] 0.00-20.00 sec 111 MBytes 46.5 Mbits/sec receiver
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-20.00 sec 145 MBytes 60.9 Mbits/sec sender
[ 4] 0.00-20.00 sec 145 MBytes 60.9 Mbits/sec receiver
So int seems speed is the half, when 2 devices are in the wifi. Full speed with 1 anten is about 70 in the N network, so it seems plausible.
I dont know why it had 4 retries once again… no idea why.
also no idea why sending and receaving are so different…
Nice to understand a little bit more of this things, tanks all vor help!!