Very low internet speed with Kabel 1000 Mb contract

[clara-tenkerian]

Hello,

Sorry for writing in English but it's difficult to discuss this in German or with customer service over the phone.

We have recently switched to Vodafone (Red Internet & Phone 1000 Cable U) but we constantly have problems with the internet speed. Since we've had to work from home this past year like most people, we chose the highest speed available. Although we were not expecting to get wifi speeds of 1000 Mb at all times, we never even reach half that speed. We've had at best around 3-400 Mb (rarely) but we mostly have under 100 Mb and many times even less than 50 Mb. 

We think the problem might be the router (Arris-sent by Vodafone) since the speed from the server to the modem is usually fine. Also, when we restart the router, the speed is sometimes temporarily improved but it fluctuates and reduces again eventually. We normally have 2 laptops connected and 2 mobile phones but even disconnecting the mobile phones from the wifi during work hours is not making much of a difference. We think our internet package of 1000 Mb should easily be able to handle 2 laptops. 

Is it possible that the router has a defect? We've only been using it for 1-2 months but we've had problems from the beginning. Please let me know what to do to improve the speed. Paying for 1000 Mb seems pointless if we don't even reach 10% of that most of the time. 
Best regards,

Clara