I have a problem with my HP Win10 64bit laptop, the wifi connection is not stable and disconnects whole the time.. Sometimes the connection is weak but sometimes very good, even though the router is 2-3 meters away from the laptop... I'm using the same wifi for other devices, but there isn't problem with them..
What do I do?
If other devices - presume, smartphones and/or tablets - have a good connection from you router and you only have problems with the laptop, I'm afraid you have some problem with the wireless adapter of your laptop. There should be no reason not to have a perfect signal 2 - 3 meters avay from the router, without any wall or structure blocking the signal.
A very easy procedure to check your laptop is to take it to some public hotspot or try to connect it to a friend's WiFi and verify how it works.
If the problem is the wifi adapter, should not be too complicated to repair it. Normally the internal wireless adapter is a small USB device connected to an internal USB port and opening the case of your laptop, it can be replaced. If replacement is not the same model as your original, you only need to install a new driver to get it working.
You just should be sure that the problem is the wireless adapter.
Now, may I ask you how do you know that the connection is weak or strong? Did you actually measure the connection rate or are you evaluating it through the download rate?
I ask this because what you call a weak connection might be some application using your connection, some as "innocent" as Windows Update or a malware using your computer as bot, using all your bandwidth to connect to its bot-net. It sounds like a joke, but it's not. One very nasty one is called "poweliks" and it's been around a couple of years now. When everything is fine and then all of a sudden your internet goes haywire it might be something like this. Maybe you might do a scan with the free version of Spybot
Download it and update it before scanning
Update to question:
Hi, thanks for the answer.. As a "weak connection" I mean when the wi-fi bar (or whatever it's called) is empty (and sometimes disconnect) even though I'm over 3 meters away from the router, then it goes back to full, but the internet is still slow or there is no internet.
Update to Answer: That should rule out the possibility of some not specified application or malware using up you bandwidht. My advice is, check if it's an internal problem of your laptop. If you can't afford to pay reparation service, you can buy a USB wifi adapter. Find a mini USB, less probable that movement should damage it while you use it.
Only as an example, not as ad for Amazon, see this one:
PD: Asker considered the answer to his problem as very satisfactory but finally never specified if he solved the problem and how he solved it.