I've been looking for an answer for months, haven't gotten anything conclusive to this day, so I'd really appreciate your input. I live in a corrupt country, where companies never deliver what they promise and constantly use shortcuts on everything possible. My ISP is leading the way on that front. It offers 20Mbps download / 5Mbps upload speed and the numbers are true only if I test the bandwidth with Ookla choosing my city as the test point. If I test the speed on any other server abroad (but close to the country I live in), the speed drops to 0.30/ 1.2Mbps and obviously I can't surf the net well; even searching in google and opening ookla site takes forever. It's a very common issue, it happens 3-6 times a week and it can last for hours, usually days, no matter how many times I reset the cable modem. Eventually it goes back to normal, but it does happen too often. The ISP can always hide behind this ookla test set to local server, because although everyone has doubts about the reasons they can't open any page, nobody cares to choose any other server to test their bandwidth or any other bandwidth measuring website for that matter (all the ones that are not based on ookla show extremely disappointing results). I would really appreciate if someone could explain if it's just another way my ISP manipulates these results locally or whether it's a normal phenomenon where the bandwidth suffers such a downfall. I don't know enough about networking and I couldn't find anyone reporting or addressing the same issue online.
P.S. I do have a fast computer and I do monitor the percentages of memory/CPU used, so it's not about that.
Thank you for your help!