Why does my router say it can do up to ac2600 but it only does 802.11ac

[ricky2.1]

I have a D-Link router and it is a AC2600 MU-MIMO WIFI Router. I know what is said on the box is theoretical but i can't even stream 4k or even 1440p so easly. I'm not sure if its my modem or if it is because i live in a condo and all the other signals are interfering with my. I am debating whether to ask my mom to pay more monthly for a better network or do some more research on my own to see what is going on. by the way I am 17 so i still have a lot to learn and i just got into this a few months ago so i'll need a lot of explanation.

 

[USAFRet]

Having mom pay for a better connection will not improve your WiFi performance.

What you need is a Cat5e cable, direct to the router.