Sound like a Problem with signal. Maybe not enough signal power or too much noise.
Best would be to contact the support. If you’ve Internet from UPC, they can look up the signal with their remote tool.
If there is a problem, a technician has to come by to readjust the signal on your socket.
Don’t worry, there are people on the support who have english skills even if there isn’t an option to choose from in the hotlinemenu.