Can't get into the Wi-Fi?

I bought a used laptop and I can only access the Internet with the lan cable. It doesn't work wirelessly because it says I should enter a security pin. I only have the password of my router. I don't know any other reasons

The security pin means the router password

I enter that and then comes, it could not be connected

Either the password is incorrect or the previous owner has installed a "child lock" for the WLAN - ask for it

Is the Wi-Fi also from your router?
Are you coming into the WLAN with another device?

Yes, I come in with a cell phone hotspot

Okay, so the Wi-Fi works first!
You want to dial into this WLAN with your laptop.
At some point you did this with your cell phone - and with this pin you can also do it with your laptop.

That is the problem I get everywhere in the wlan only not on the laptop after I have made new system on it Windows 7

And before you installed the system, did you also use your laptop?
If you select the right WLAN on the laptop and click on Connect, then you will be asked for the password and then you will give the same password as in the other devices and then what is the error?

Do you also enter the password for the other devices? Is it really the right one? You can see that in the router itself!