Greetings Laurentiu,
If there is a lag every three seconds, like a pause, but then resumes afterwards then let's check to see if there may be any other app running on the phone that may be using system resources. This may affect the performance of the Canon Camera Connect app when using the remote shooting mode.
In some cases, the wireless connection may be a factor. For example, if you've connected the camera to a local wireless router which the phone is connected to then let's try using the camera's access point instead which allows for the phone to connect directly to the camera wirelessly. This will help eliminate any bandwidth issues that may occur from a local wireless router that other devices may be connected to.
You may also test a different mobile device to see if the performance improves, like testing the remote shooting with a different phone or tablet.
One thing to note is that the live image presented on the Canon Camera Connect app may lag behind what is actually seen through the camera due to the overall bandwidth limitations of a wireless connection. For more responsive performance for remote shooting, we recommend on using the EOS Utility software with the camera connected to a computer through a USB cable.
