There is a newer Kernel, try to install.
It may be a driver problem. Please check Internet connection is way too slow - #6 by limotux
and [SOLVED] WiFi Very Slow, Eth. Is OK (though it was on Artix but it is still Arch as Manjaro.)
Try the new kernel and drivers.
I hope this helps.
P.S. My machine is Lenovo as well, but other model, above worked for me.