Use an internet benchmark tool with the same browser you use for video-conference at Deepin, (Ookla, AT&T, some page like those), and run 3-5 benchmarks at their servers. Check if the results are the correct for your internet plan. If they are, so everything is well and the problem is on that page or with the browser, try installing another one (I suppose you're using Chrome, try with a light one like Min, Midori or Pale Moon). A problem with one device, like ethernet or wifi can appear, but with all devices... More probably that your internet works bad or your router isn't well configured (Ports for example), on that case your ISP provider need to be called.

And, to see if PC is the problem, try installing I-Nex or CPU-G and then run a benchmark test to see if some of your PC's components aren't working as they must.