Oh dear. Where do I start.
5G is not 5GHz. It is merely a signalling protocol for cellphones.
You are talking about WiFi.
Further on, there are caps on how much you can radiate at certain band. Those caps are there for a reason. 2.4GHz in Europe is capped at 100mW. 5Ghz (for channels 36-48) are capped at 200mW.
There are more 5GHz channels (UNII-2 etc.) which might or might not be allowed in your country and might be allowed with more power.
2.4GHz in a urban environment is often overcrowded and barely usable. 2.4GHz offer only three non-overlapping channels and as soon as your neighbour sends on same channel, your router needs to wait (regardless of SSID or password).
And last and most important: your phone radiates maybe 50mW. Your Laptop will radiate 100mW. Raising output power beyond regulations on router side only will only make it shout louder but your device will not be able to shout back. Thus you get typical "I have three dots but Internet works bad" issue. WiFi is created to work nice with these parameters. Raising it beyond only works if both sides can do it (and is illegal to boot).
If you need to Skype from your garden, get a AP (access point) and wire it to your router. And do use 5GHz channels. It is much much better than 2.4GHz. You can use ac protocol, have more bandwidth and less interference.