AC1200 wifi router R6120 problemas de conexion wifi

not much to go on. Just a router model. 

There's a support site with access to manuals, firmware, install guides, etc.
Go to https://www.netgear.com/support/
Type in your model number and from there it'll take you to the above.
Its a great resource to start with.

 

To get a hold of support. Click on "MyNetgear" at the top.
Register an account (or login) and then the device.
From there you can start the support process. Keep in mind that its only free for the first 90 days.