I would recommend a powerline adapter over an extender
https://www.amazon.com/NETGEAR-PowerLINE-1200-Gigabit-PL1200-100PAS/dp/B00S6DBGJM
One plugs into the wall by the router and connects with ethernet. The second you plug in near the laptop and then you can use an ethernet connection off of that. It sends your internet through the powerlines in the house. Have had good luck with those in the past in large houses.
The Netgear LAX20 lacks band 71 support. You iPhone is probably a late model (unspecified), so it probably supports band 71.
That is probably a critical omission for T-mobile services, especially if your trying to get cellular data reception in a basement. Band 71 is around 650MHz and Band 12 is around 720MHz. These bands are considerably better at penetrating walls compared to where most cellular data operates: Band 2/4/66/30 are all around 2000MHz.
Are you in a T-mobile Band 12/700mhz A block market? https://www.tmonews.com/700mhz-lte-map/ If not, then we have probably found the cause: lack of Band 71 on your LTE modem.
Is the storage unit on the same electrical service as your apartment? I'm thinking no, but in the off chance the answer is yes look at AV2 homeplug powerline networking equipment. https://www.amazon.com/NETGEAR-PowerLINE-1200-Gigabit-PL1200-100PAS/dp/B00S6DBGJM/ This is an excellent way to get your network past several walls that WiFi cannot penetrate, but the power outlets need to be on the same service panel (the technology cannot cross a transformer). I have seen it cross electrical meters in multi-family dwellings before though... so maybe?
Hey folks - sorry for reviving an old thread, but I wanted an opinion. I'm currently at 100mbps up and down but am going to upgrade to 1Gbps. I'm using an Airport Extreme router at my drop to handle Wifi for all the devices upstairs. I have a very large house (I'm not rich, we just got lucky) and since wifi doesn't work well on the first floor I'm using powerline networking to bridge downstairs. I'm currently using this setup:
Downstairs I've got a second Airport Extreme for my downstairs network.
I'm considering replacing the *upstairs* wifi unit with https://www.amazon.com/gp/product/B019WAQMVY/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1. This is a slightly higher version of what was recommended below. But maybe that's overkill. A few weeks back my connection speed went to crap and a restart of the Extreme fixed it. That doesn't mean the hardware is dead, but if I do replace them, would that ASUS make sense?