We're a small business and need a router upgrade - what should we look for?

Hi Reddit! I hope this is posted the correct place.

I'm from a small business and is the most tech-savvy guy there (which doesn't say a lot, we're an art book publishing company) and we need a router upgrade. Our router (or the ability to connect to it) has constant failure. Our ISP says their connection to the router works fine, so the problem is with our local connection. We called the router company and went through a length of fixes, none of them seeming to work. We've both moved physically around and done a bunch of technical attempts until they couldn't help us anymore. The problem, according to the company, seems to be the amount of traffic in our vicinity. I believe them, I can literally see 62 connections atm. They know our model and believe upgrading to something with a bit more power would work. (Our router is pretty cheap.) We need to keep the connection wireless as we constantly have guests, contacts, authors etc. passing by and we need that stuff to run as smoothly as possible.

(Also before you ask, our internet connection speed is not the problem, we're just 5 people in the office on a large day and it's 100 dollars a month)

So here's the problem. I don't know how router power works, so I'm not sure what I'm looking for. This seems to be a good list https://www.techradar.com/news/best-small-business-routers but I want to be sure whether any or all of these would be appropriate.

Best regards, some incidental IT guy :^)

(Also I'm Danish so if some sentences are nonsensical or unclear, don't be afraid to ask.)