Need help picking out an antenna

I’m looking for some advice on an outdoor antenna that would work with my Verizon LTE Router—it's basically the standard home gateway from T-Mobile.
I’ve ended up in this pretty bizarre situation, honestly. Without an antenna, I can't catch a decent 4G signal at all. But get this—if I take the little antenna that came with the Huawei unit and just hold it up against the window, I actually start picking up 4G, whereas when the antenna stays inside the house, nothing happens. I’m stuck in this weird dead zone between a cell tower and a hill, and I have no clue what's happening with the signal physics here. The folks over at T-Mobile actually gave me a specific direction to point an antenna toward, and once I did, it actually worked...
I’ve been asking around a bit, and someone suggested https://mikrotik.com/product/MTAS-5G-15D120. Now, I’m not sure if I need something even more powerful, though I wouldn't want to spend more than about $333.

Thanks in advance. (And sorry if I’m barking up the wrong tree here—if I'm in the wrong place, my bad.)

That antenna won't work because it’s tuned for 5GHz WiFi, not the 3G/4G frequencies we need.
Check if you can find two Iskra P56 units at a decent price—they cover all the mobile bands.

wearymason4 said:That antenna won't work—it’s built for 5GHz WiFi, not the 3G/4G frequencies you actually need.
See if you can track down two Iskra P56 units for a decent price; they cover all the mobile bands we deal with here.

What about something like this?

Is that what you meant by the Iskras? I see they have two different versions out there...

So, the P56 setup uses two identical LPDA antennas to crank up those speeds. They’re meant to be installed at a 45° and 135° polarization so they can run in MIMO Diversity mode.
That one in the plastic housing from the link here is also an LPDA, just a single one. Just so you know, all LPDA types usually top out at a max gain of about 8 dBi.
With the P56, you get 10 meters of coax for both antennas, whereas that one wrapped in unnecessary plastic only comes with a measly 55cm.