Thanks for the answers.
@TheUberOverLord
1.I have static ip address and I have set the dhcp range of router correctly.
2. I have upnp disabled.
3. I have wired connection(tried both ethernet+wall socket and poe).
4. I have set ftp server of the router disk, so the banwidth is 1gbps. Moreover, I have tested the disk can read/write 30MBytes/sec.
5. I dont have any problems with reboots.
Today, I tried with different router. The results were the same. Yesterday I tried with ethernet and wall socket. So, the poe switch and the poe splitter are not the problem.
Moreover, I downgrade to other versions of firmware and I upgraded to the last again. With all firmwares I had the same problem.
I tried with ddns and only tcp connection. Again the same problem.
I tried with different programs and different browsers.
I port scanned the camera and I found that it has the port 65534 opened. Is it normal? Because, I read on internet that this port is for hack attack.
Additionally, the foscam support said that the videos seemed normal.
The only thing I did not try was wireless connection. The only thing I think is if the black cable of camera has problem, because I push it on installation.
These are the ping times of the camera to my pc: