How to find the root cause for slow networking?

Occasionally I find the connection to the internet is very slow. I tried checking fast.com and speedtest.net, finding the latency is a bit high and download/upload speed is not good. For instance,

Code:// fast.com
Your Internet speed is 150 Kbps
Latency Upload
Unloaded Loaded Speed
213 ms 794 ms 7.4 Mbps

// speedtest.net
Ping ms
177

Download Mbps
0.41

Upload Mbps
4.22traceroute command returns the result like below
Code:1 _gateway (192.168.22.11) 2.391 ms 2.485 ms 3.249 ms
2 10.183.244.254 (10.183.244.254) 79.211 ms * *
3 10.158.61.2 (10.158.61.2) 83.330 ms 83.321 ms 10.158.62.8 (10.158.62.8) 83.313 ms
4 10.158.50.10 (10.158.50.10) 83.306 ms 83.298 ms 83.289 ms
5 10.158.50.11 (10.158.50.11) 83.280 ms 83.272 ms 83.263 ms
6 33.sft.net (210.65.12.10) 83.254 ms 75.159 ms 79.532 ms
7 30.sft.net (220.128.12.18) 84.891 ms 30.sft.net (220.128.12.18) 23.353 ms 48.016 ms
8 32.sft.net (220.128.1.5) 43.710 ms 31.sft.net (220.128.1.6) 67.085 ms 32.sft.net (220.128.1.5) 72.087 ms
...
13 * * *
... # the rest of traceroute (between 13 and 30) merely prints * * *
30 * * *
How can I check to see if the problem is my side or at the isp or anything else? Or any other places I can check as well? Thanks

My env
Code:Debian testing
Kernel 5.10.0-8-rt-amd64