Hey @safanasev,
Welcome to the Community! I'm going to help you with your connection right away.
Let's look for a solution so you can be online again without disconnection. You indicate that you've already performed a number of steps but I'll take you through them. First of all, I would like to ask you to switch off your modem and unplug it from the wall socket. Wait 30 seconds, your modem will reconnect. Does that not help? On our Community you can find some tools to get your fixed internet working again. Look here for the explanation: https://forum.tele2.nl/vast-internet-188/info-what-to-do-mijn-vaste-internet-doet-het-niet-80725.
When the connection breaks down, are you connected via Wifi or via wired internet? If it is via wifi then it is possible that your wifi is not optimal. The strength of the Wi-Fi depends on a number of things. For example the distance to the modem, a blockage (walls) or a neighbour's network. We cannot change everything, but we can optimise it! On our Community you can find some tools to improve the range and stability of your wifi. Look here for the explanation: https://bit.ly/T2WifiTips. Especially adjusting the wifi channel is usually the solution. This will strengthen your wifi!
Please let us know if it helped you. The Community is here for you!