What to do with Wi-Fi on a laptop?

Question

Iron

Hello.
A laptop (Lenovo G570, age - 3 years) has recently begun to work poorly with a Wi-Fi network:

1. slow data transfer;
   
2. does not connect to the network, but sees it (signal level - 3/4);
   
3. does not see any network (but they are definitely there).
   

I think it's a problem with the Wi-Fi card, I want to buy an external one - will it help? If so, do you need anything else?
PS OS - Linux Fedora 22 WORKSTATION, Microsoft Windows 7 "Starter" - works equally badly.
PPS Wi-Fi neighbor, but the problem is definitely not in it.

Answer 1

Somehow, all three points contradict each other a little. Just a little ...
I would, for starters, disassemble and check what's wrong with the antenna. Maybe the wire was just interrupted due to an unfortunate location near the hinges of the lid. Or maybe the old card has some kind of hardware problem with age.
I can't imagine how it is possible to adequately answer the question "whether it will help?". Under certain circumstances, if the problem is exactly in the built-in card, it will help.