trouble connecting to wi-fi

The vast majority of Wi-Fi problems are caused by difficulties in your specific Wi-Fi environment, not by defects in your computer or its software.

To get an idea what your Wi-Fi environment looks like, hold down the option key while clicking on the Wi-Fi Icon on the menubar, and you get a snapshot like this older one:

post a screenshot or answer these questions:

what is PHY mode and channel?

Transmit Rate?

RSSI or signal AND at what distance from Router?

How many networks are showing?

Note that also on that menu, there is an item named Network Diagnostics. It can be helpful for making some recommendations about your network, Monitoring your network while in use, and has some helpful displays available.

You are in the very busy and interference-prone 2.4GHz band. There are THREE clear channels for 802.11n in this band. Fastest baseband data rate is about 65Mbits/sec, and you are using two antennas to get about twice that rate. your signal of -43 less typical background noise at -80 leaves a very good signal-to noise of -37.

Thirteen other networks showing makes it impossible to establish and maintain a good fast connection in that band. If your Router is set to "automatic" channel selection, it has given up on the standard 1, 6, and 11, and moved to an overlapping channel on channel 10 (or perhaps you or the ISP technician deliberately moved it there).

If the ISP's Router does not provide the 5GHz band, you should seriously consider adding your own dual-band router, and networking with their or replacing their Router, like these setups:

in this situation, Wirelessly extending an already hopelessly overloaded 2.4GHz network would not be possible, but a Roaming Network would help a lot.

lets take a look at what you have available to you, and the competition.

Hold down the Option key and click on the Wi-Fi Icon on the menuBar. Choose network diagnostics and stop.

From the window menu, choose Scan.

You get a report that looks something like this one.

this is interesting to start to look at competition, but it does not show signal "spread" very well. For that, I like the presentation shown by the inexpensive Utility called WiFi Explorer:

(drag and drop on Preview to see much larger)

You have very good signal strength. I would not hesitate to walk away from the noise of your neighbors and move to the 5GHz band.

With most Routers, you can force the issue by giving the 2.4GHz and the 5GHZ different network-names. Then you can selectively connect to the name you want to try.

Try it out before you spend the money on a new Router. Then look at it with the Option-Wi-Fi panel and see how it does. The Mac seems to see the 2.4GHz signal strength and connects you there, unless you take deliberate action to use 5GHz.

a newer Router would add 802.11ac, which uses even more antennas to get higher speeds. Most MacBooks that can run 10.13 can use 802.11ac.

addon to Grant's post:

update HighSierra to the latest (10.13.2).

there are two with a strong signal. seems that all are on the same channel???

You need to stretch the window out so that you can see what is on each channel. It says there are 12 in all, but you need to stretch the window down as well to see the rest.