No internet on laptop, if certain mobile phone is also connected to Wi-Fi, what to do?

Since my brother recently lost his cell phone, he got our old cell phone as a replacement from our uncle. This is such a Chinese non-brand smartphone. We also use a Wi-Fi repeater.

Now it's like I have massive internet problems on my laptop when my brother comes home. The laptop has at irregular intervals always "no internet" but is connected to the wireless internet. If I disconnect myself briefly from the Wlan and then reconnect the problem is solved.

In addition, not only me but also my brother has a connection problem and we have to pull out the repeater and put it back in order to solve it.

What do we have to do to make the internet work normally again?

Can you turn off the Bluetooth from the phone. That helped us. But I do not know the reasons for that. Maybe it will help you too.

But I do not know the reasons for that

Bluetooth has the same frequency as WLAN 2.4 GHz, so BT might be able to use it. To disturb.

Either the strange not brand device disturbs the reception, as bensw19 has already recognized so correctly, or you have given the setting of the Internet connection somewhere a static IP address and it comes to a ip address conflict if both devices are in the network…

As far as the latter is concerned, you should make sure when assigning static addresses that they are outside the DHCP range, in the Fritz box, for example. Would that be the final digits 100 to 150 and of course each static address only for a device is awarded.