Как я могу получить сигнал WiFi внутри морозильной камеры?

Getting through the walls is going to be nearly impossible - they effectively make a Faraday cage... Your best bet is to get an AP that can tolerate being inside the freezer and run it in with a hardline Ethernet cable.

The easiest thing to do is probably going to be to drill a hole through the wall of the freezer (or use an existing one), and run microwave coaxial cable through the hole. Back when I worked for a wireless ISP, we used Times Microwave LMR cable for this (we were going outside the building, not into a freezer). On the freezer side, you put a low-gain outdoor-rated antenna (omni or panel, depending on location in freezer, check the radiation pattern to see that it covers the freezer), connected to the coax. Make sure to weather-seal the connection(s), you don't want water getting in.

This setup works for outdoors, your freezer will probably be a much nicer environment. No UV from the sun, etc. You can put a plastic guard over the antenna if you need to protect it from impact. Metal will block the signal.

Seal the hole in the freezer wall you run the coax through. You just want to stop air leakage. The efficiency impact on the freezer is going to be unmeasurable, as long as you don't have a lot of air leaking. (It's a ¼–⅝" hole compared to a surface area a hundred thousand times larger).

On the other side of the coax, you attach your access point. Use only one of the antenna connectors, and configure the access point to only use that antenna. (APs are usually not designed to have the two antennas on one AP in different locations, and it will cause issues).

Your coax can be basically as long as you need. Each foot of the coax causes some loss of signal strength, if you go long enough (hundreds of feet) you'll have to switch to more expensive (thicker) coax, and eventually add an amplifier inside the freezer. An outdoor amp will be fine, unless this is a -40 walk-in freezer, but keep the power low. If you need a setup with an amp (and you really shouldn't), find a wifi contractor.

Use a different access point to serve clients outside the freezer. Use the same SSID, and connect the two access points to each other with Ethernet. Each AP should be on a non-overlapping channel (use 1, 6, and 11 in the US, unless you really need more than 3, then 1, 4, 8, 11). Clients should roam between the two seamlessly.

If you have any budget for this, the folks who install satellite dishes should be able to do all of the cable & antenna work. Won't take them too long, either, so it shouldn't be that expensive. Or you could find someone who does wifi networks to handle the whole thing.

As was said in the comments to the other answer, you can set up an AP outside the freezer, with a remote antenna inside the freezer. Some routers have multiple antennae, or allow for additional antennae to be attached, for additional range/coverage. If the AP has at least two antennae and they use BNC connectors, all you have to do is mount the AP outside the freezer, disconnect one of the antennae and run a length of BNC coaxial cable into the freezer with the antenna reconnected to the other end. Some measure of frost protection to prevent shorting would be advisable; you could wrap the connection in electrical tape, or give it a shot of that Flex-Seal stuff. This should get you connectivity both inside and out, without having to have two APs (and thus having the problem of dropping and reconnecting to different wireless APs as you go in and out).

1. Connect a long ethernet cord to an access point or router
2. Open the freezer and walk into it, make sure theres slack on the ethernet cable
3. Attach the access point to the ceiling
4. Enjoy your wireless signal inside of your freezer

Test if you get cell phone service inside the walkin. You could possibly set up a personal hotspot inside the walkin. Unfortunately this would not be running on the same network as the one outside. In that case a VPN might work.