Bandwidth, throughput and latency
Bandwidth describes capacity, throughput is the useful data rate observed by the application, and latency is the time a small round trip takes. A healthy network needs more than a high peak speed.
Measure rather than guess
Run both directions, review one-second samples, and compare tests made from the same primary device. The diagnosis shows its supporting evidence and certainty.
Repeat tests carefully
Background transfers, device power saving and changing radio conditions affect results. Repeat a few times under comparable conditions before drawing conclusions.