There's this handy tool known as tracert you can run from a command prompt.
I'd suggest using it, at least a few times, on at least a few different targets.
It will produce something that looks like this
C:\>tracert
www.google.com
Tracing route to
www.google.com [172.217.7.132] over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms [redacted]
This is you.
2 3 ms 1 ms 10 ms network-065-189-187-119.bcs.swo.rr.com [redacted]
This is your local ISP stuff
3 13 ms 7 ms 7 ms be21.pltsohae01r.midwest.rr.com [redacted]
This is stuff between you, your local ISP and where you're trying to go.
4 11 ms 7 ms 8 ms be25.clmkohpe01r.midwest.rr.com [redacted]
This is stuff between you, your local ISP and where you're trying to go.
5 24 ms 16 ms 23 ms bu-ether15.chctilwc00w-bcr00.tbone.rr.com [redacted]
This is stuff between you, your local ISP and where you're trying to go.
6 19 ms 23 ms 23 ms bu-ether11.chcgildt87w-bcr00.tbone.rr.com [redacted]
This is stuff between you, your local ISP and where you're trying to go.
7 16 ms 15 ms 15 ms 216.3.52.41
This is stuff between you, your local ISP and where you're trying to go.
8 16 ms 16 ms 20 ms 216.3.52.54
This is stuff between you, your local ISP and where you're trying to go.
9 16 ms 16 ms 16 ms 216.239.56.130
This is stuff between you, your local ISP and where you're trying to go.
10 16 ms 16 ms 16 ms 72.14.237.130
This is stuff between you, your local ISP and where you're trying to go.
11 28 ms 28 ms 29 ms 209.85.143.171
This is stuff between you, your local ISP and where you're trying to go.
12 28 ms 28 ms 28 ms 216.239.48.94
This is stuff between you, your local ISP and where you're trying to go.
13 25 ms 21 ms 21 ms 108.170.240.97
This is stuff between you, your local ISP and where you're trying to go.
14 21 ms 21 ms 21 ms 216.239.54.127
This is Google's local ISP stuff.
15 23 ms 21 ms 21 ms iad30s08-in-f4.1e100.net [172.217.7.132]
This is www.google.com
If you see *'s instead of ## ms, this particular hop has either timed out or is configured not to respond to these. In most cases, the issue is not at your end, nor is it at the target end. It's stuff in the middle that is the issue.
If those ## ms are exceptionally high (greater than 40 ms) there is something going on that that particular hop. It might be traffic related, it might be hardware related - it might be mice nesting in a router hub in a field somewhere.
And those hops? Those are the routers along the way your data has passed through to get from you to where you are going. In this case, I passed through 15 of them to get to Google.
You can't fix this. Your ISP can't fix this. Your target cannot fix this. But by your powers combined, this can get reported to the right people who can either fix it, or at the very least let the people who can fix it know it needs fixed.
