Zend certified PHP/Magento developer

New router on network, pages take around 5 seconds to start loading

I installed a new router on my home network (D-Link DIR-882) to try to improve wifi signal quality, since my ISP modem (Huawei HG8245Q2) was having a very unstable connection through wifi.

I followed all steps in the D-Link wizard. Speed and stability has been good, however all pages take around 5 seconds to start loading (on Chrome it shows “Resolving Host” on progress bar), then the pages load normally.

The biggest problem is on the phones and the Smart TV, which take a very long time to connect, and sometimes they completely fail to connect.
I just took a Speedtest through my phone, and it took more than 30 seconds to find a server to perform the test. When it started the speed was great, though.

Anyone knows what may be causing this issue?