insp14 5490 - scan hardware not working - internet speed reducing dramatically

i have bought last week an Inspiron 14 5490 - with windows 10 home version 1909

i have issues with the wifi-internet - the speed reduces over time dramatically from some 80Mbps to 1 - 5 Mbps and it collapses totally. when i do a speed test it says from time to time  'a Socket error cocured during the Upload test

my family members do not have issues with the internet (it is stable for their lenovo and apple computers as well our ipads do not have issues)

i have tried to run the Scan Hardware test, but if fails every time and stays at 0 %

can somebody advise what to do?