Did you test the speed with C1200? What's the difference between it and old router?

If you did not set any QoS or bandwidth control, it should limit the speed.

Do you watch Netflix or Youtube? 

Hello, the speed of the internet works well, it is the content shared through the Lan network, they are video files.

What's the firmware version of your router? 

How do you share files? Do you use USB drive?

I do not know what version of the firm it is, the multimedia content is through a network PC.
The content is through LAN. the strange thing is that with an old router the multimedia files go smoothly and with this tplink every 3 minutes you have to load buffer.

You can try to use different computer and different cable to have a test, the cable should be cat 5e or above.

The link speed is very important as well, check the link speed on the computer, make sure it's not the link speed limit the lan speed.

If your firmware is not the latest one, can try to upgrade it.

https://www.tp-link.com/en/faq-315.html

The cables are Cat5 and the firmware is updated to the latest version.
The problem still exists, when watching content of 720p quality or higher comprated by the network the videos stop and do not work, however with the old router, zte f680 the videos work perfectly, what can I do?

@Brutal 

You will need to go into the router management website, i.e. http://<router IP> and do some basic management. Additionally, visit tp-link support website and download the product manual for the router. Furthermore, do review firmware downloads and FAQs section too.