weird router issues

[albert86]

So, I have two routers, one is a modem+router provided by the ISP, the other is a netgear nighthawk r6700. I live in Taiwan, while the netgear is from america (i don't know if that will affect anything as i am networking noob, but i thot i shud mention it). So, heres the issue: my mom has an old laptop that can only receive 2.4ghz signal or something like that. If i connect (wirelessly) to the ISP router, speedtest by ookla gives my something like 80-90 mbps (my internet connection is 100mbps i think). If i connect to the netgear router, i only get 40 to 50 mbps. I hav no clue why that is, and i hav been sitting here for an hour trying to sort out this issue. I imagine that the netgear router shud be up to par with the ISP one, not worse. BTW, i have them set at different channels so thats probably not the issue.